Hi Red and welcome, though I'm sorry it's a hydrops that has brought you to the forum. I don't think there's an easy answer to your questions - how long it takes to clear up varies from weeks to quite a few months, and the end result is unpredictable as well though sometimes vision can actually improve after a hydrops. If you go to
www.keratoconus-group.org.uk/sitev3/features.html you'll find an article on Hydrops and Keratoconus written by one of the senior optometrists at Moorfields.
For the moment, it's a question of hanging on in there. I've never had a hydrops episode, but there's quite a few people on this forum who have, so hopefully they'll be along soon to give you some encouragement.
All the best
Anne