The communal hut that the castaways build after their individual huts fail has a dirt floor. However, after the storm clears, the hut is floating in the lagoon. The people would obviously be in the water, not safe and dry inside.
The whole reason Mary Ann went to go into her and Ginger's hut was because something she was cooking was burning. Yet when the hut collapses due to Gilligan recklessly trying to get the door open, it was clearly empty of anything.
The hut they all took shelter in wound up out in the lagoon somehow, but when the Skipper goes outside after the storm, we don't hear a splash.
Ginger claims she made makeup from berries that were highly unlikely to be found on a tropical island. If she did in fact find crushed red berries for lipstick how did she not know if they were poisonous? Blueberries for eye shadow would have made for a clumpy and dark eye shadow that a woman of her stature would not be wearing. Yet both she and Mary Ann wore fake eye lashes the entire time on the island. Eventually those lashes would not have held on.