The warmth and transparency of the waters of San Matias Gulf and particularly the Bay of San Antonio and its zone of influence, are due to a combination of oceanographic and atmospheric aspects, with the peculiar geographical conformation of the coastal zone. The amplitude of the tides, the circulation system of coastal currents, high summer temperatures and lack of rainfall are contributing factors to this phenomenon, unique in the Patagonia.
Tides are cyclical movements experienced by the sea level and that are reflected particularly on its coasts. Originating in the gravitational pull that the moon and the sun exert on the mass of ocean water, the tides in this area experience daily changes in sea level of between 6 and 9 meters wide. This difference in level determines that the entire surface of the Bay of San Antonio is flooded twice a day and is also dried a lot of hours per day.
In times of low tide, solar radiation warms dramatically tidal flats of the bay, also producing an increase in water temperature of the tidal pools and channels that remain in water. This stored heat is then transferred by convection to the mass of water that flooded the Bay of San Antonio in times of high tide, causing an increase in average water temperature.
The high temperature in the summer months leads to greater evaporation of water entering the Bay of San Antonio, resulting in a greater accumulation of salts in the body of water in the system.
The marked difference in salinity and temperature with water from the streams of general circulation in San Matías Gulf (colder) and the flow direction of these coastal currents outside the bay, determine that the water exchange between the two masses is minimal. Thanks to this combination of factors, the same body of water is recycled and repeatedly circulated in the coastal system of the Bay of San Antonio and surrounding area.