Previously, I had been looking into “rugged laptops” that are waterproof and shock resistant among other things. They tend to cost about $3,000 but you can find them used on ebay for $100-200 (they have the hard drives removed for confidentiality because they are ex-military).
But another digital nomad told me “why don’t you just get a waterproof bag”? After noticing how technologically out of date the rugged laptops seemed, I am now thinking about getting an ultra-light “ultrabook” (like a Macbook Air) with a waterproof bag in case the ocean creeps up on my backpack at the beach or another surge of water rushes over the gunwale while I am snorkeling.
Indie traveler has a good discussion of the travel laptop options.
Aqua Quest Storm makes a “100% waterproof” case for $35.
If you need something a little more rugged and shockproof, check out Pelican’s laptop cases for about $65.
Amazon has Macbook Air’s used for as low as $300.