I am unaware if its the same in earlier versions of them game ( I don't use boats that often)
When getting into a boat the huger bar should stay visible
The hunger bar disappears when getting into a boat, still able to eat and raise the the hunger , but it is not visible till you get out
1.Get in a boat
2.Look?
Duplicate of MC-14640. If you have not, please search before reporting issues to see if your bug has been reported already.