The new Sonim XP3 Enduro, claimed to be the only GSM cell phone that is fully capable of being submerged in water.  With an antiglare and shock resistant screen you can be sure that it will withstand almost any condition it is exposed to.  It has a Mil-810F certification for exposure to salt, fog, humidity, thermal shock and of course transport shock.  Check out the spec highlights and what others have to say about it below:

Features and Specs:

1. Dust and micro particle proof
2. Operational under extreme thermal conditions
3. Water/liquid proof
4. Durable Keyboard Mechanics/extra wide buttons
5. Impact (drop) protection
6. Extra-loud speakers for use in noisy environments
7. Resistant to shocks and vibration
8. Extra-long Battery life
9. 3 year Unconditional Guarantee

Links on the Sonim XP3 Enduro:

Sonim XP3 Enduro [Sonim]

Sonim XP3 Enduro is tougher and meaner, goes underwater too [GSM Arena] :

The phone can withstand more shocks and drops than its predecessor and can also be fully submersed for 30 minutes up to a meter deep. On top of this, it is certified to withstand a drop to concrete from as high as 2 meters. [GSM Arena]

Crazy Johns Launches Sonim XP3 Enduro [Gizmodo]

Sonix XP3 Enduro Review [Cnet]