missing water?? in floating on the bedrock?? dafuk?

Put the summary of the bug you're having here

What I expected to happen was...:
floating normally with my boat

What actually happened was...:
i falled down to the bedrock level

Steps to Reproduce:
1. navigate to the middle of the sea with a boat
2. put the pause and save game
3. close the game
4. resume previously saved game
5. you re' falling in a natural mine and in lava, and in bedrock... i don't know how can i explain