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1 INTRODUCTION

According to the latest data from the World Health

Organization (WHO), the global number of drowning

fatalities in 2021 was approximately 300,000 [15].

However, WHO highlights that these figures are likely

underreported by 30 to 50 percent, as they do not

account for drowning deaths related to water

transportation, environmental disasters, self-harm, or

assaults.

In 2023, Bulgaria reported 5,753 rescues from

drowning, with the number of drowning fatalities

significantly decreased compared to previous years.

Despite these positive trends, drowning remains a

critical public health concern, with more than 30

individuals drowning every hour and 300,000

drowning deaths recorded in 2021 alone. Nearly half of

all drowning deaths occur among individuals under

the age of 29, and one-quarter involve children under

the age of 5. One promising approach to mitigating

these fatalities is the development and implementation

of intelligent systems that assist lifeguards and provide

beachgoers with the necessary information to make

informed decisions regarding the safety of specific

beach zones. The deployment of smart buoys is one

such method that holds potential for reducing

drowning statistics.

Various types of buoys are employed across a broad

spectrum of applications, ranging from military

purposes, such as monitoring the sea surface and

underwater environments [3], to environmental

monitoring systems for remote ocean observation [4],

[2]. Additionally, buoys are utilized as integral

components of safety systems designed to assist

lifeguards in preventing drowning incidents [8] and for

real-time drowning detection [7]. They also play a vital

role in enhancing navigational safety and maintaining

environmental standards in port areas [1], [10], as well

as supporting research efforts in marine science [6], [9].

Design and Implement an Automatic Smart Buoy

System for a Bulgarian Safe Beach Areas – Part 1

I. Dimitrov

, I. Iliev

, D. Hristov

, D. Dinkov

& T. Mavrodiev

Nikola Vaptsarov Naval Academy, Varna, Bulgaria

Technical University of Munich, Munich, Germany

ABSTRACT: Drowning is the third leading cause of unintentional injury-related deaths, accounting for 9% of all

injury fatalities, with over 300,250 cases reported annually by the World Health Organization (WHO) in 2021.

Addressing this issue necessitates the implementation of affordable and accessible safety measures at local

beaches. This paper presents an innovative, cost-effective automated system designed to improve beach safety

through real-time environmental monitoring. The system consists of three primary subsystems: sensors,

information processing, and action mechanisms. At its core are smart buoys, equipped with sensors and

communication modules, which transmit data to an onshore station and a cloud-based platform. This platform

processes, stores, and monitors the data against predefined thresholds, generating alerts when necessary. A web

application provides real-time data access, enabling fault monitoring, system operation forecasting, and

performance optimization.

http://www.transnav.eu

the International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 19

Number 2

June 2025

DOI: 10.12716/1001.19.02.05

382

In European coastal areas, buoys are widely

deployed to delineate safe bathing zones, primarily to

protect swimmers from watercraft, separate swimming

areas from potentially hazardous regions, and signal

water conditions. The use of buoys in these contexts is

governed by both international and national

regulations, which aim to ensure public safety and

safeguard the marine environment.

Furthermore, the beach flag system, managed by

lifeguards, provides an additional layer of

communication to beachgoers. This system uses visual

cues to convey current sea and weather conditions,

alerting individuals to potential risks and ensuring

their safety.

Beach flags are routinely adjusted to reflect

significant risks such as rip currents, high waves,

strong tides, and adverse weather conditions, all of

which pose hazards to swimmers. The integration of

smart buoys that collect real-time data on these

environmental risks greatly enhances beach safety.

These buoys supply lifeguards with critical, up-to-date

information, facilitating faster response times to

hazardous situations and improving the accuracy of

flag warning decisions. By automating environmental

monitoring, smart buoys contribute to more efficient

lifeguard operations and offer enhanced protection for

swimmers, ensuring a safer beach environment

overall.

In this paper, the authors present an innovative and

cost-effective solution in the form of an automated

system that utilizes a network of smart buoys and

onshore stations. The system is designed to collect,

store, and analyse critical environmental data, enabling

precise interventions by lifeguards and, when

necessary, fully automating the flag signalling process.

The implementation of this system holds the potential

to substantially improve safety within designated

beach areas, providing real-time monitoring and more

efficient responses to emerging risks.

2 REGULATIONS

The regulations governing the use of beach buoys in

Bulgaria exhibit some minor differences from broader

European standards, although they generally share the

same objective of ensuring swimmer safety and

managing water traffic. In Europe, similar standards

are established under the EU Bathing Water Directive

(2006/7/EC) and ISO 20712-3:2024 safety guidelines

[13]. The yellow colour code is universally adopted for

buoys that mark safe swimming zones. Despite these

broadly accepted norms, the International

Organization for Standardization (ISO) does not

provide specific rules or recommendations regarding

the operation, replacement, or maintenance of buoys in

beach zones.

While Bulgarian regulations largely align with

European standards, there are notable discrepancies in

certain areas, such as the distances used to delineate

swimming zones and the precise responsibilities

assigned to local authorities for buoy maintenance and

supervision. Although the use of buoys to demarcate

swimming areas is stipulated by the Bulgarian Water

Act and local regulations, instances of improper

application of the colour code or incorrect buoy

placement, such as the use of 11 L water bottles painted

yellow (Fig. 1), are not uncommon.

Figure 1. Water bottles used as buoy

3 OPERATIONAL MECHANISM

The automated system developed by the research team

seeks to improve the situational awareness of

lifeguards while maintaining cost-effectiveness. The

primary objective is to provide municipalities with

limited financial resources an affordable alternative to

the less efficient plastic bottles currently used for

marking swimming zones.

The smart buoy automated system (Fig. 2) consists

of three core components: hardware, data processing,

and action mechanisms. These elements work

synergistically to offer real-time environmental

monitoring, thereby enhancing safety measures at

coastal areas.

Figure 2. Automated system – basic diagram

The hardware of the system incorporates a range of

sensors and custom-built data collectors, including

anemometers, temperature sensors, UV sensors,

accelerometers, and gyroscopes, among others. These

sensors are strategically placed both on the buoys and

at onshore stations, such as lifeguard posts, to ensure

comprehensive environmental monitoring.

The data gathered by the sensors is transmitted to

onshore stations, where it is subsequently sent to a

cloud server for storage. Once the data is stored, it

undergoes a processing phase to extract meaningful

information.

The processed data is then presented to users via

interactive interfaces, providing real-time insights into

environmental conditions. In addition, the system

utilizes the processed data to generate alerts for

hardware malfunctions or communication issues.

Furthermore, it can trigger notifications for lifeguards

to update the flag status or, in the absence of lifeguards,

autonomously adjust the flag as needed. This

automated flag signalling function is particularly

critical in unguarded beach areas, where human

intervention may not be available, potentially saving

lives.

It is important to note, however, that individual

judgment and personal adherence to safety guidelines

should always complement the system's

recommendations, even in the absence of a regulatory

body.

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4 CONSTRUCTION

The smart buoy is designed with a complex, modular

structure aimed at enhancing functionality and

simplifying maintenance. To create the desired model,

the buoy's body was 3D printed using PLA+ material

with a 10% infill (Fig. 3). To ensure waterproofing and

increase durability, Dichtol (a polymer that forms a

waterproof layer) and resin (a viscous substance also

used for waterproofing) were applied to seal any

openings, effectively protecting the internal

components from water ingress and enhancing the

buoy's longevity.

Figure 3. Smart Buoy model – 3D printing process

The modular design (Fig. 4) incorporates several

distinctive features, with the three primary

components being the main body, the chamber, and the

cylinder. The main body is equipped with angled slots

specifically designed to house solar panels, optimized

to achieve maximum performance based on Bulgaria’s

geographic location. Each slot is connected to a channel

that leads to the chamber at the bottom of the buoy.

Additionally, a central hole is included for the precise

placement of the cylinder, with an extra rib ensuring

proper alignment.

Figure 4. Smart Buoy model – general view

The central hole is sealed by a lid that includes a

special groove to house an O-ring, providing airtight

waterproofing. A dedicated hole at the bottom of the

buoy accommodates the water temperature sensor,

and a specialized hook attachment point is included,

allowing the buoy to be securely tethered by a rope

(Fig. 5)

Figure 5. Smart Buoy model – water temperature sensor and

hook attachment point

The chamber is located at the base of the buoy and

is connected to the solar panels via channels running

through the body, as well as to the water temperature

sensor. Both the solar panels and the sensor are

permanently fixed, and the chamber is sealed to

prevent water ingress. Its lid is designed with openings

only for two sockets, which connect the chamber to

other electronics housed in the cylinder.

The cylinder, comprising a lid and body, has a

specific orientation for placement within the buoy, a

critical feature for ensuring proper alignment of the

two sockets that connect the water temperature sensor

and supply power from the solar panels to the

microcontroller. This modular configuration not only

ensures correct placement but also facilitates ease of

maintenance for lifeguards, enabling quick and simple

replacement of the electronics in the cylinder in case of

technical issues.

4.1 Sensing Subsystem

The developed sensing subsystem is physically

divided into two parts: onshore and offshore sensor

circuits, each collecting different types of data.

On the buoy, measurements related to position

tracking, such as acceleration, angular velocity, and

spatial orientation, are made using the onboard 9-axis

inertial measurement unit (IMU) of the Arduino

NANO 33 BLE microcontroller. Additionally, water

temperature is sensed using a waterproof DS18B20

temperature sensor.

The static onshore station collects data related to

environmental conditions, including wind speed and

direction, through a custom-made plastic wind

indicator. This device detects the orientation of the

rotor using an electronic compass that measures the

magnetic field of a magnet attached to the moving part,

alongside an anemometer that utilizes a Hall sensor for

revolution counting. Furthermore, the system is

capable of analysing air quality, humidity, and

temperature using the BOSH BME688 air quality

sensor. An additional feature of the onshore station is

the detection of UV radiation index, providing

valuable environmental data for both lifeguards and

individuals on the shore.

4.2 Communication

The communication scheme is modelled into long-

range and short-range infrastructure for effective data

exchange.

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Data transfer between the buoys and the onshore

station is facilitated by Bluetooth Low Energy (BLE)

technology, which is available on the Arduino NANO

33 BLE. To extend the communication range to

approximately 200 meters, modifications to the

underlying Mbed OS are necessary. These adjustments

include the use of the maximum transmit power (+8

dBm) on the nRF52840 microcontroller and enabling

the hardware-optimized Bluetooth Long-Range

feature to improve signal reception.

The BLE protocol supports the Generic Attribute

Profile (GATT) specification, which will be

implemented in the initial phase of the project. The

communication hierarchy consists of central (client)

and peripheral (server) devices. In this setup, the

onshore station acts as the central device (client), while

the buoys function as peripheral devices (servers) (Fig.

6). The client device periodically scans for nearby

peripherals and requests the data they have available.

Figure 6. Normal communication between the buoys and the

station

In the event of a lost connection between a buoy and

its designated onshore station, the communication

system is designed to support a MESH profile (Fig. 7)

for auxiliary data exchange directly between buoys

and stations. In this mode, a cluster of connected

devices will relay information from a buoy in need to

the nearest operational onshore station. The primary

advantage of utilizing this operation mode is that it

ensures continuous data flow even in the event of

partial system failures, preventing data loss and aiding

in the identification and localization of malfunctions.

Figure 7. Example of broken connection between a buoy and

the station – switch to MESH profile

Long-range communication for data transfer from

the onshore station to the central information system is

facilitated by a GPRS module installed on the onshore

controller board. Although based on the now-obsolete

2G cellular standard, GPRS remains widely available

and widely used due to its compatibility with most

mobile devices. Notably, GPRS supports IPv4, which is

used to transfer data from the onshore station to the

central information system via a REST API. Once

received, the data is aggregated, summarized, and

displayed on a web interface for further analysis.

4.3 Energy Management

Both the onshore and offshore systems are designed to

be autonomous and self-sustained in terms of energy

management. To achieve this, a set of solar cells with a

nominal power output of 1 W will generate electrical

energy during the day, part of which will be stored in

a lithium-ion battery for use during the night.

To maximize power production, the solar cells (one

on the stations and four on the buoys) are oriented with

a tilt angle corresponding to the latitude of the target

location, with a southward orientation for locations in

the northern hemisphere and a northward orientation

for locations in the southern hemisphere.

Power consumption measurements were made for

the main electronic components in both configurations,

and the average power requirements of the systems

were calculated. When supplied with 5 V, the

microcontroller board required 350 mA of current

during Bluetooth Low Energy (BLE) data transmission

and only 2 mA in an idle state. Thus, the total power

used for communication can be calculated as follows

[5]:

( )

0.0833

1 12

5 350 1 2

155

trans

comm trans trans

comm

T min

P V mA mA

P mW





=  = =

=   + − 



(1)

where:

Pcomm – Power Consumption;

ηtrans – Transmission Efficiency (the fraction of time the

system spends in transmission mode);

T- Total time;

ttrans – Duty Circle.

The interpretation of the result means that the

system spends about 8.33% of the time in transmission

mode and about 91.67% of the time in idle mode.

This indicates that data transmission occurs only for

a small fraction of the total time, which is typical for

energy-efficient systems

Furthermore, sensors that consume more than 1

mW of power, such as the water temperature sensor in

the buoy and the air quality detection circuit, must also

be considered. These sensors are essential for real-time

environmental data collection and significantly

contribute to the system's overall energy consumption.

The water temperature sensor continuously monitors

temperature variations, while the air quality detection

circuit measures various environmental factors,

including humidity, temperature, and the air quality

index. Both sensors are critical to the system's

functionality and must be factored in when calculating

the total power demand, ensuring that the solar power

system and battery capacity can support their

operation over extended periods, especially during

low-light conditions or at night. Their maximum

power consumption is as follows [11], [12]:

385

688

18 20

5 5 25

5 1.5 7.5

BME

DS B

P V mA mW

=  =

(2)

Thus, the total energy consumption is 180 mW for

the station and 162.5 mW for the buoy. A 3200 mAh Li-

Ion battery cell, managed by a DFR 0559 solar power

management board, serves as a buffer between the

energy produced by the solar cells and the energy

consumed by the electronics in each device. Based on

these figures, it can be estimated that the devices would

operate for approximately 2 to 3 days without any solar

energy input.

4.4 Web Application

The smart buoy system will be accessible through a

dedicated web application (Fig. 8) [14], which is

organized into four main sections: an informational

page, a data-access map, an API (Application

Programming Interface), and an administrative panel.

Figure 8. Web Application – main page

The informational page provides details about the

project, the team behind it, and any awards or

recognitions it has received. The map section is

especially useful for general users, enabling them to

select beaches with the most favorable conditions for

their visit. This feature enhances the beachgoer

experience, promoting safer and more enjoyable

summer tourism in areas where the smart buoy system

has been implemented.

The API page allows users interested in accessing

the data collected by the system to obtain access tokens,

providing personalized data retrieval options for

further analysis or integration with other platforms.

The administrative panel is reserved for the project

team, providing real-time monitoring of the buoys. It

offers live updates on data, battery levels, and the

operational status of each station or buoy. This ensures

that the team can efficiently manage and maintain the

system's functionality.

To further facilitate user access, QR codes linking to

the web application will be placed in key locations

corresponding to areas monitored by the smart buoy

system. This will allow users to easily access up-to-date

information on beach conditions and enhance their

overall experience.

5 DISCUSSION

The current study focused on designing and

simulating an IoT-based smart buoy system aimed at

enhancing safety in beach areas. Further research and

development are planned to address critical aspects of

the system's performance and reliability.

A subsequent paper will explore the physical

implementation of the system, including the 3D

printing of components, the assembly process, and

testing within a controlled environment. This

upcoming study will provide detailed insights into the

practical challenges encountered during system

construction and initial deployment.

Moreover, a dedicated paper is planned to

investigate data transmission resilience, specifically

addressing scenarios involving communication loss

between individual buoys and the shore station. The

analysis will include the behavior of the system under

such conditions, focusing on the underlying algorithms

– particularly the MESH network approach – to ensure

continuous data flow and operational stability.

Future research will also encompass field

deployment in a real-world, operational beach zone

managed by the Nikola Vaptsarov Naval Academy

(NVNA). This phase aims to evaluate the system's

functionality under diverse conditions, including

different operational modes and varying weather

patterns. The performance metrics will cover data

acquisition reliability, energy consumption, and the

system’s ability to adapt to environmental changes,

contributing to a comprehensive understanding of its

practical feasibility and potential for large-scale

implementation.

Additionally, the web application designed to

monitor and manage the buoy system will undergo

rigorous testing. This evaluation will focus on user

interface efficiency, real-time data visualization, and

system control capabilities to ensure seamless

interaction between lifeguards, operators, and the

buoy network.

6 CONCLUSIONS

Ultimately, the integration of applied technologies,

such as the proposed automated system using smart

buoys, presents a promising solution for enhancing

beach safety. By providing real-time environmental

data to lifeguards and automating flag warnings, this

system has the potential to significantly reduce

drowning incidents.

Moreover, the data collected by the smart buoys can

be further analyzed to advance our understanding of

water phenomena, such as rip currents, and contribute

to early-warning systems for natural disasters like

tsunamis. This dual benefit not only improves

immediate safety measures but also supports long-

term research, pushing the boundaries of knowledge

on coastal hazards and further strengthening coastal

safety protocols.

In the next article, the research team will provide

detailed information about the actual development of

the beach safety zone system. This will include insights

into the design process, challenges faced, and the

technical implementation steps taken to ensure the

system’s functionality and effectiveness in real-world

conditions.

Future work could focus on integrating the system

with other IoT technologies, such as water and air

quality sensors, automated traffic management

systems, and drones for beach monitoring. This would

allow for a more comprehensive analysis of conditions

and a more effective response to emergency situations.

386

ACKNOWLEDGEMENT

This research paper has received funding from project “Safe

beach zones” sponsored by Nikola Vaptsarov Naval

Academy.

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