The best waterproof thumb drive on the market is the Corsair Flash Survivor Stealth 64GB USB 3.0 drive. The military-style data transport is as fast and rugged as the planes its aircraft-grade aluminum chassis is re-purposed from. It has a hard-anodized, waterproof, shock resistant exterior to protect the top-of-the-line technology inside. All this is backed by a limited five year warranty.
The Survivor Stealth USB 3.0 is compatible with both USB 3.0 and USB 2.0 technology. USB 3.0 gives the drive additional speed, and is four times faster than traditional USB 2.0 drives. The drive has a max read speed of 85 MB per second and max write of 70 MB per second. Those speeds are a bit slower than drives specifically engineered for high speeds, but are still more than serviceable for such a rugged drive.
In addition to being fast as lighting, the Corsair Flash Survivor Stealth is rugged. Its aircraft-grade aluminum housing is waterproof up to 200 meters thanks to the use of an EPDM (ethylene propylene diene monomer rubber) waterproof seal. A molded shock damping collar makes the Survivor vibration proof and shock resistant.
In addition to the 64 GB storage size, Corsair offers the Survivor Stealth in 16, 32, and 128 and 256 GB. The drive weighs 1.3 ounces and is a bit bulky, as can be expected from a rugged drive. It has a hole to hook on to your key ring, but the hole is on the drive itself, not the cap. It unscrews in two halves, so you need to be careful not to lose the cap.
The Survivor Stealth USB 3.0 is available from Amazon for around $45.
The LaCie XtremKey is another rugged USB drive with USB 2.0 and 3.0 capability. It can withstand ten tons of pressure thanks to its metal alloy exterior. The XtremKey also holds up well against heat and water.
The XtremKey outpaces the Corsair Survivor Stealth in speed tests. A Maximum PC test found that it performed key reads at an impressive 213MB/s, taking just 3 minutes 34 seconds to write an 11GB file-copy test. The XtremKey is even bulkier than the Survivor, so it is not great for portability.
The LaCie XtremKey is available from Amazon for around $83.