Polytunnels are flimsy in compression, but clear plastic can be very good in tension and can contain a bar or so of pressure fairly easily, so it may be feasibl

Polytunnels are flimsy in compression, but clear plastic can be very good in tension and can contain a bar or so of pressure fairly easily, so it may be feasible. It was only one of the solutions I thought of for coping with storms if you are growing out at sea. The other two are either being able to reel them back onto land, or just making them short and tough, so they can just roll over the waves. The buoyancy problem isn't that difficult though as you can have counter-buoyancy that rises when they sink.