When you're below any boat underwater, you can glitch through the boat below it. At first it may seem like everything is okay and will stop you when trying to, but when you hold click the space bar to go up you will glitch through the boat.

How to reproduce

Start by crafting a boat, then go under the boat and try to go above the boat, you will go through the boat successfully.

Observations: Can glitch through boat when underwater/below the boat,
Expectations: Nothing happens and the boat blocks the way.

Also relates to MCPE-105535.