Of course, we at Boating do not accept manufacturer claims such as these until we test them for ourselves. So, ignoring the fact that the Mystic costs more than the balance in my checking account, I hastily roll up my sleeve and thrust the handheld into the river's 40-degree water. I hold it there until my hand turns blue, then pull it out-and yes, the GPS and VHF features still work. The Mystic takes a splashing and keeps on tracking. So if you accidentally drop it into the bay, you can still call mayday.