@nomerci,
They did not actually put their car into the sea.

During low tide, water recedes from shore. And during high tide, water level rises and water moves into the beach, which transforms the earlier 'dry' beach into wet/part of the sea!

The white car, was parked on 'dry' ground early (see pic 4 from the bottom). Afterwards, they did not (surprisingly) realize that water was rising round them!

By the time they decided to return, it was too late!