Is it practical? As far as I know, unless they're citizens, the countries of such coasts aren't obligated to accept them. And it's often not clear where they're actually from. Plus, what if they're from a war zone?

In the case I have in mind (people trying to get from Lybia to Italy), there's no country to speak of in Lybia currently. Even if there were and it wouldn't agree to the EU ship entering their waters, you can always get very near to the water border, inflate another raft for the people and board them on it. They'd have to sail to Lybia by themselves.

The bigger picture is that these situations would very quickly stop happening if the word spread that it's not longer viable as a way to get into the EU.

I wonder if returning them to Libya is actually better than letting them drown.

How will you tell where to ship them if they've discarded their passports?

Ship them to the shore they came from, not their home country. The whole operation could take a couple hours, not weeks/months/years of paper-pushing.

How do you find out where they came from? And is it at all plausible to survey enough of the sea to catch even half of refugees coming in by boat?