I haven't bothered to read all the responses so what I am about to say may already have been covered. Sorry if that's the case and I say this from the PoV of another life, having once been heavily involved in the insurance industry.
Insurance is a can of worms, well and truly:
• Homeowners Insurance: Statistically Insurance Actuaries (glorified mathematicians and one is more "odd" than the next) can tell you, almost to the nearest single monetary unit of your choice, what the payout figure is going to be for the "homeowners" bit of the insurance risk on their house in a particular area, The risk does go up exponentially if the house is rented but it's still statistically viable. Adding strange stuff such as, in our case, SCUBA gear adds to the risk and is not statistically viable. IOW, they're guessing. Informed guessing, yes, but nevertheless guessing, They also know that every proposal they issue has wording on it along the lines of "have you ever had a policy refused or cancelled?" They base their risk assessment on the fact that your homeowners policy is much more valuable to you, as it should be, than the odd 10K claim, that your claim is therefore likely to be much more "legitimate" than that of the person holding an individual policy. You think that Insurance Companies don't talk to each other? Think again, I am living proof that they do so, so if you answered "no" to that question above when the correct answer would be "yes", good luck to you. Odds are that you'll be caught out and, if you are, then your policy all-of-a-sudden becomes null and void.
• Specialist SCUBA Insurance (of the sort provided by the likes of DEPP). The statistics are simply not there, yes, they can make educated guesses, but statistically the actuaries are groping in the dark. As mentioned abve, people making claims under this type of policy have an unfortunate habit of "embellishing" the claim. How often have you heard "I'll just claim it back on insurance"? I'm essentially on the Insurance Companies' side on this one, if only because they have a "duty of care" towards their other customers because claims have the unfortunate habit of increasing premiums. That's very bad PR for any Insurance Company.
Consider that the premium you pay on your insurance is a loss and you're the "right" kind of Policyholder/Customer. One who only claims when something extraordinary happens which, I suppose, includes a flood. I haven't insured my camera gear (for underwater purposes) in any number of years and, premium wise, I'm well in front. I recognise, though, that sh1t happens and that one of these (not so) fine days I'll get well and truly caught out. It's, however, the path I've chosen, yours may vary.