I have one of those zip-lock bag type covers for the iPad, but only use it as a backup, so it's all I felt I needed. They are about $20. In 3 or 4 years now, I've put it in there maybe twice to have it in the cockpit.
However, I always have my iPhone in my pocket and actually find I use it to check distances, weather radar and even my track/location when I can't easily see the chartplotter from my perch on the side of the pushpit. For it, I bought the LifeProof cover and really like it. If I were to use the iPad on deck more frequently, I would probably get a LifeProof cover for it.
The only minor downside is picture quality. It remains very good, but you can tell a bit of a difference. Otherwise, it's pretty cool how they maintained all functionality inside a waterproof case, even charging and headset plugs.