I had a Neptune catch a wing tip and cartwheel, tearing the wing off. The rudder & elevator servos, which were side-by-side were different brands. One was a Hitech 425, the other was a Bluebird 621 (or some number like that), Both werestandard size.

When I got home and removed the servos, the Hitech was full of water, but the Bluebird was dry. It has O-rings and is waterproof. Later I tested one by dunking it in a glass of water and operating it with the receiver on the table. No leakage. I am putting Bluebirds in all my seaplanes.

Photos of Bluebird servo in water glass showing 2 positions of the servo arm. I actually cycled it for a couple of minutes.
Photo os servo after removing from water. Note there is no water in the case. The transparent black/gray plastic helps.