[eternityforest]

I don't see why that would make them hard to detect. As long as you're above the waves a few percent of the time you should have no trouble getting a signal out, and if you have an antenna you could probably get GPS too, plus, there's some pretty powerful dyes you could release periodically, LEDs that could be seen easily if it's just a few meters of water....

Seems like it would have to be criminally bad design without any kind of signalling at all, to be near the surface and not found within hours.