I also suggest as soon as possible opening up the receiver and servos, blotting them dry with a paper towel and then use a heat gun to further dry and then set in a dry atmosphere for a day or so before closing back up. Completely agree with the need to run the engine as soon as you get it to the shore.

Finally, and probably most importantly - you should never, repeat never, plan that your retrieval technique is swimming out to the plane. You should always have a boat available for this. I've seen folks have to swim until they were out beyond their swimming capability due to a combination of their initial burst of adrenalin to get to their precious plane and a breeze blowing the plane ever further from shore. Never heard of a loss of life from this, but it seems like an unnecessary risk.