When he asks for the snails, she bends over to get the snails. Her shirt is clearly wet in the middle. In the next shot the shirt's only wet on the sides.
Which scene are you referring to? I just saw this movie last night and I remember that there were about 3 scenes where the girl goes into the tank for sea snails. In the first scene, her entire chest gets wet and is still wet when she gets out of the tank!
When she returns to the counter, her breast area is still wet, but the area between her breasts and the rest of the shirt below isn't. Almost the entire front of her shirt dipped into the water, so the whole front should be wet, not just the breasts.