When I cover a part with water with a block, the water then remains in the block even though there is no water around it.

Thank you for your report!
However, this issue is Incomplete.

Your report does not contain enough information. As such, we're unable to understand or reproduce the problem.

You are welcome to create a new ticket about your issue with more detailed information.
However, please review the Bug Tracker Guidelines and be sure to search for existing issues before writing a new bug report.

Quick Links:
📓 Bug Tracker Guidelines – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki