Eye relief is not an issue. They only way you would notice a slightly changing eye relief is if you find a target in the scope on low power and then turn the mag up... and that’s a sub par way to manipulate a rifle.
Yes, they are waterproof. I haven’t seen any thread about one leaking due a boat spill- do you have a link?
Durability, etc... It’s a good bet that no one will abuse a scope as much as the dozens of SWFA HD’s I have seen. I have multiple 2.5-10x NXS’s sitting in a closet, while 3-9x SWFA’s are on guns. Those I shoot with have the same, and yet are choosing the SS over the NXS’s every time.
I'm curious if you have any more insight on the above given that almost two years have passed since you wrote it (28th August, 2018).
The SHV is solid. They are not built to be literally bombproof, but they are good. No one cares about a static zero more than I, and I have no issues using an SHV save the SFP.