And the sea disappeared suddenly.

Ocean water mysteriously receded from various beaches in Porto Alegre and Tramandai, Brazil and Punta del Este, Uruguay. A tsunami underway?

On August 11, 2017, the ocean water almost disappeared along beaches in Punta del Este, Uruguay:

Just several hours later on August 12, 2017, the same weird phenomenon occurred along beaches in Porto Alegre and Tramandaí in Brazil:

Waters recede ahead of a tsunami, so you understand people running for their lifes, when they observed this phenomenon. When there are no signs of large quakes and tsunamis, weather specialists believe that offshore storms and wind direction may also trigger a similar effect. For example for Punta del Este in Uruguay, when there are storms with a south wind, the waters rise and hit the rambla. In contrast when the storms are accompaied by a north wind, the water recedes.

But this time such a giant and widespread ocean receding effect is unprecedented!