Sorry, but this was impossible to capture as a screenshot, so the summary explains everything.
MCPE-64105
You break blocks above your head when swimming in a one high space
Resolved
Duplicate
1
Thank you for your report!
We're already tracking this issue at MCPE-57257, so I will resolve and link this ticket 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:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki