Personally, I've studied a LOT of virology. Is it plausible a zombie outbreak could happen? Not likely.
Is it likely that the human race will be completely annihilated by some sort of virus/pathogen? EXTREMELY likely. We've had plenty of close calls already. All we need is a common virus nowadays to mutate that had perfect resistance.
Either way -- it's good to prepare for a "Doomsday Event".
I myself am readily equipped for such a situation. I have multiple medical kits, rifles (and a large stockpile of ammunition), enough MRE's and food to last a year (but if rationed correctly -- much longer), two generators, etc. TONS of gear and supplies.
When I'm back home, people often say how "May there be mercy on the soul of the person who dare trespasses or attempts breaking into your home."
People know I take care of business.
Anyways, about your plan. You'd only want 3-4 people max. People who are solid and WONT turn on you no matter what. Also, living on a rig would be very deteriorating on your mental health. Trust me. Life at sea gets old fast. And you'd have to constantly worry about any masses of storms on your back step -- all of which you said.
Also, weapons wise -- I'd have to go with a .22 long rifle actually. More particularly -- the best rifle I've ever owned, a Ruger 10/22. Seriously. These things never break, jam, etc. A brick (525 rounds) of Remington (128 grain) hollow points only weighs about 5 pounds. You can carry a LOT of rounds, it's VERY cheap, extremely accurate (just went varmint hunting today with it. Hit every shot with surgical precision), etc.
Best. Rifle. Ever.
For gathering food/some aspects of protection. I mean, .22 hollow points REALLY mess people up. I see more .22 injuries in the ER when I do clinical than any other gun shot wound. The worst part about a .22 hollow point is usually -- it mushrooms into several sharp lead points alright. But a lot of the time, it never goes all the way through and will literally rip up your gut. Pretty nasty stuff.
But for human/zombie defense -- a Mossberg 500 or Remington 870 is where it's at. Both are incredibly reliable, munition is CHEAP. Incredibly cheap. And -- you can't really mess up with a shotgun. No precision aiming needed, point and shoot.
Anyways, just my two cents.