The latest hard disk drive from A-Data is waterproof for up to 30 minutes of submersion.
That makes the SH93 one of the few hard drives that can be dunked completely into a body of water. A-Data says the SH93 can sit in 1 m of water for up to a half hour. It's also shock-resistant, enduring the "military standard MIL-STD-810F drop test," which subjects the hard drive to a variety of environmental conditions. Data transfer rate is 30 MB per second.
Other hard drives that are completely waterproof include the ioSafe Solo and R4 and SentrySafe Fire-Safe. The latter is also fireproof, but both are considerably bulkier than the ultra-portable SH93, which measures 5.1 x 3.8 x 0.76 inches. While those larger hard drives seem designed more for protection of data at home, A-Data says the SH93 is designed for students, travelers and sports enthusiasts.
The real competition, I think, comes from Hitachi's SimpleTOUGH, a rugged-looking hard disk drive that also uses a 2.5-inch interface, and withstood being rolled over by a one-ton commercial truck. Both models also have USB cables attached. Though Hitachi's drive is merely spill resistant, instead of fully-waterproof, I think you're mostly looking to avoid spill damage with both models unless you live in a flood-prone area.
Even then, I've yet to see a computer that can be completely submerged in water, so you may have bigger problems on your hands if your home takes on water.
A-Data's staying mum on pricing and release date at the moment, but said the SH93 will come in capacities of 250 GB, 320 GB, 500 GB and 640 GB.
