How much?
I also agree that a standard non-marinized notebook will fare well below decks on the nav table, with a sheet of non-skid material under it, and it at sea, a strap (velcro, etc) holding it down. I guess if it's gonna get soaked with salt water, it'll die and a marinized one might survive for a while, but we keep ours below and dry. The rest depends on your budget to a large extent, since you can get notebooks from under $800 to $5000. Since you're going to use it for business also you want enough storage for both. Suggest 300 or greater mhz processor, over 2 gig storage (get 4 if you can since you'll load all your digitized charts) and an active-matrix screen. If you would like to save a few $$$, a factory refurbished unit is a good choice, from Egghead or Damark online. I use "The Cap'n" software, which does it all, "all" includes stuff you'll probably never need unless you're operating the QEII! You can get a less expensive program, but if you can afford it, this is the best, as it has, in addition to navigation, maintenance logs, ship's inventory, etc, etc.