Can human remains buried at sea 30+ years ago realistically be recovered and given a more traditional, land-based burial?

If you are talking about this kind of burial at sea… then realistically, no.

For a number of reasons. Most burials at seas, from what I understand, are of the scattering of the ashes kind anymore. So there’s that.

Once a body is exposed to the sea, its going to start decomposing just like it does in the ground in traditional cemetery. That’s the whole point. In twenty thirty years, there would be very little left.

The only time it wouldn’t, is if the body were to settle on the bottom where the oxygen and temperature is so low, that it delays decomposition. But that’s rare and unpredictable.

Then there is the in practicality of being able to locate a body, and bringing it back up. Both would be very difficult and expensive, long past the point of not being worth it.