Rarely, when you dismount from rideables like boats, they can vanish. You cannot interact with them, but the boat itself is still there, as you cannot place blocks on that spot. If you reload the game, the boat will appear again.
As an added note, it seems that if you dismount from a boat near land, you can sort of go through blocks.
Related issues
duplicates
Comments
[Mod] OcelotOnesie
migrated
Thank you for your report!
We're tracking this issue in MCPE-108568, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki