In Minecraft 1.19.2 if a boat falls from any height onto a floor with flowing water on top of it, the boat will continue to fall through that floor. The flowing water must be from a source at least 5 blocks away, if the water is higher than half a block, the boat will float as usual. This bug happens with chest boats too. If there is a body of water directly beneath the floor, the player can ride the boat and move through the floor without getting hurt. Mobs riding the boat will move through regardless of water below and get hurt. It does not matter from which height the boat is falling or weather it is alligned to a block.

steps to reproduce:

• fill a 1 layer thick solid floor directly on top of a body of wather
• mark a spot to drop the boat on and put a water source at least 5 blocks away flowing towards the spot.
• summon a boat or chest boat above the spot and watch it fall through the floor
• remove the water below the floor to see that the boat no longer carries you through the floor

this behaviour might be interesting for some contraptions moving boats, but it looks very wrong and may be exploited to overcome indestructable floors or roofs in a protected multiplayer scenario. At least the player moving through blocks should be patched. Thank you