Jake,

My life jacket pocket is not particularly waterproof and it's been totally submerged for minutes at a time... So I begin to wonder if the leakages are occuring when the GPS is in a place where it is getting impacted or distorted while being submerged or inundated. I could definitely see it being more likely to leak if it is being squashed by my knee on the tramp while it is getting hit by a wave, etc.. Just a thought.