How do you know if the seawater is in good condition for bathing?

Discover the crucial link between beach conditions and seawater quality for safe bathing. Guaymas & San Carlos beaches data reveals risks of contamination. Let's act now to protect tourists & preserve coastal beauty through proper management & infrastructure.

How do you know if the seawater is in good condition for bathing?
Crystal-clear waters during pre-Easter at Miramar beach, Guaymas, Sonora, offer safe bathing conditions. Credit: Gabriela Torres Mundo via SECTUR México

When planning a day at the beach, one of the most critical considerations is the condition of the seawater. The health and safety of beachgoers are directly impacted by the microbiological quality of the water. Unfortunately, determining whether the seawater is suitable for bathing is not as simple as a visual inspection.

A comprehensive assessment involving laboratory studies and water sample analyses is necessary to make an informed judgment. However, researchers have conducted such studies, shedding light on the potential risks associated with bathing in contaminated seawater.

The Impact of Beach Conditions on Water Quality

Before delving into the scientific data, we can raise some pertinent questions that provide valuable insights into the beach's overall condition. Factors such as the presence of restrooms, showers, and trash containers, the number of visitors, the presence of dogs, sewage discharges, and nearby boats can significantly affect the microbiological state of the beach.

A worrisome combination of no sanitary facilities, no waste disposal, high human and animal density, sewage discharges, and nearby boat activity is indicative of a beach with compromised water quality. Such beaches often harbor faecal microorganisms that can lead to gastrointestinal and acute respiratory febrile diseases, posing potential health risks for beachgoers.

The World Health Organization (WHO) has set benchmarks to gauge seawater contamination, using enterococci as indicator bacteria for faecal pollution. If seawater contains between 41 and 200 MPN (most probable number) of enterococci per 100 ml, there is a 1% to 5% risk of gastrointestinal illness and a 0.3% to 1.9% risk of acute respiratory febrile illness. As the concentration exceeds 500 MPN/100 ml, the risks increase significantly. For instance, contamination between 201 and 500 MPN/100 ml raises the chance of gastrointestinal illness to 5% to 10% and respiratory illness to 1.9% to 3.9%.

A Wake-up Call for Guaymas and San Carlos Beaches

Analyzing the data from beaches in Guaymas and San Carlos, Sonora, reveals a cause for concern. At Miramar beach in 2017, enterococci concentrations were below 100 NMP/100 ml before Holy Week. However, during the holiday period, concentrations spiked to over 2,000 NMP and remained high throughout the summer and winter. Similarly, San Francisco beach and Los Algodones beach both saw values exceeding 1,000 NMP after Easter and summer. At El Cochórit beach in Empalme, values higher than 2,500 MPN were observed during the same periods.

Authorities have taken measures to certify these beaches as clean destinations, as evident from pre-Easter water samples with optimal results. Collaboration with institutions like the Centro de Investigaciones Biológicas del Noroeste (Cibnor) and the Coordinación Regional Guaymas del Centro de Investigación en Alimentación y Desarrollo (CIAD) has been crucial in this regard. Nevertheless, a concerning pattern emerges when tourists arrive at these beaches – water quality rapidly deteriorates, necessitating a reassessment of the influx and beach management strategies.

Recommendations for a Safer Seawater Experience

Influx Management: Proper planning and regulation of beach visitors during peak seasons can help reduce the risk of contamination.

Basic Infrastructure: Adequate facilities such as restrooms, showers, and waste disposal bins must be available to maintain cleanliness and hygiene.

Hygiene Regulations: Implementing and enforcing rules about maintaining personal hygiene before entering the sea can significantly contribute to water quality.

Addressing Leakage Problems: Addressing sewage leakage and drainage issues near the beaches is essential to prevent contamination.


Ensuring safe seawater conditions for bathing is a collective responsibility that involves the efforts of authorities, beach managers, tourists, and local communities. The findings from Guaymas and San Carlos beaches serve as a wake-up call, emphasizing the importance of proactive measures to preserve the pristine beauty of these tourist destinations. By addressing the challenges and investing in sustainable solutions, we can provide visitors with an enjoyable and safe beach experience while safeguarding our coastal ecosystems for future generations.