I have a vacuum on my Nauticam housing, and I still have it insured.
I use USAA's VPP (valuable personal property) coverage...no deductible replacement. It wouldn't help me if I get a flood on a trip, but it will get me a new camera for my next one. It's very inexpensive for everything I have covered, and gives peace of mind. This is especially true when the airline decides to make you check a carry on full of photo gear b/c all the bins are full.