Village's snow houses have sea as floor

On my first visit to a village which is situated on tundra and snowy beach biomes and ends at the sea, two of the snow houses had no floor but instead were generated  on the surface  of the sea.  I could walk in, dive and swim out, and come  up on the open sea. 

At night one of these houses was occupied by two villagers.  One slept on the bed and the other trod water next to it.  The other house was vacant, although the water was shallower there.

External and internal views of the worst affected house follow.