In bedrock the mines are filled with water

This is actually a feature.

Thank you for your report!

However, this issue has been temporarily closed as Awaiting Response.

Is this still an issue in the latest version? If yes, can you please add it to the affected versions (or mention it if you are not the reporter)? Also, does MCPE-141624 describe your issue?

This ticket will automatically reopen when you reply.

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📓 Issue Guidelines – 💬 Mojang Support – 📧 Suggestions – 📖 Minecraft Wiki

Cleaning up old tickets: This ticket had been set to 'Awaiting Response', but has not received a response from the reporter (~3 months+) so is being closed as Incomplete. If you feel this is still a valid issue then please comment, or create a new ticket following the Issue Guidelines which includes steps to reproduce the problem.

Quick Links:
📓 Issue Guidelines – 💬 Mojang Support – 📧 Suggestions – 📖 Minecraft Wiki