If you own the property outright, you are not required to buy flood insurance. For many of us on the oceanfront, it is VERY expensive to insure against flood damage. For example, I was quoted nearly $12,000 to insure my small home, and was able to get it down to $9,200. And even that had a very high deductible and excluded any damage on levels of the house that were less than 12 feet above sea level. So I cancelled after a few years and decided to self insure. It's a gamble, but I only really lose if the house is completely destroyed by a massive hurricane.
It can also be a bit tricky to prove flood damage (i.e., damage from water coming from below through high tides or storm surge) and other water-related damage (i.e., rain damage to your home from high winds that took off a portion of the roof or shatter a window or simply seep through the seams in your house).
The best advice I've seen in all the comments is to check with an insurance expert, and would add that you should talk to other owners near the property you are considering.