Because of where you live, there are a couple of effects that you won't be able to change.
1) No matter how much grading you do, if the water rises sufficiently enough, it will permiate UP through the soil. In short, the only way you can 'prevent' this is to raise the house. 2) It's very common for homes near lakes and high water tables to be built with crawlspaces that allow them to flood. In a sense, the crawl allows water to rise and pass through w/o any 'hindering' objects (like a poured wall, or something.)
BUT, you hit an important point: If the water comes in contact with the joists, THAT'S a problem. Get out of there as fast as you can. Also, if the crawl isn't draining properly, and water is allowed to 'sit' in there, then you will get mold and higher-than-normal humidity levels inside the home. BUT (again) if the crawl fills with water in your described worst-case scenario, and it doesn't come in contact with any 'rot-able' part of the home, AND it drains 'relatively quickly' then the crawl is doing what it's suppose to be doing. It's thus allowing water in, it's keeping it AWAY from the rot-able parts of the home, AND it's letting the water OUT.
One last thing: Find yourself a reputable ASHI Approved Home Inspector in your area. Find an Inspector that's VERY familiar with your type of home. Talk to other home owners around the Shore that had their homes inspected. Don't use the Realtor's inspector! There could be a conflict of interest. Oh, and ask your neighbors how they found their Inspector. (If it 'came with the Realtor's recommendation', personally, I'd skip them. DO spend a few hundred $$$ for an inspection. It's CHEAP $$$ when you're about to spend 10's, possibly 100's, of thousands of dollars on a new home over the next 20-30 years. Check out this recent Thread in which I, among others, talk about ASHI Inspectors so you get some 1st hand info. Attic ... Good luck, and let us know if you need more info.