For some context, the fact that ocean ruins can generate on land is covered by MC-126520. The fact that they can still contain water when on land would be the bug here.
This ticket is a duplicate of MC-242630. I've altered the description of MC-242630 to mention that this can cause, in some cases, the said water to not flow.
For some context, the fact that ocean ruins can generate on land is covered by MC-126520. The fact that they can still contain water when on land would be the bug here.