Are gliders overkill for costal work?

I've talked to some people using Slocum gliders in less than 50 meters of water, complaining that they are difficult to control, and they are worried they will not return. Is this really the best tool on the market for this? Is there another way to do this kind of work? I know there are small AUVs out there, but I've heard they lack the range needed for these missions.

Is this a larger problem others are experiencing as well?