Have not fished in rain but mine did go off while in storage under front deck from moisture that eroded the salt tablet. But! At least I know it works! I believe you are supposed to change out the canister and the salt every two years or so and pressure check the vest by inflating the vest once a year. Never go without mine. No matter how good a swimmer you may be if you hit you head on the way out of the boat ya might not swim so good. Good luck....
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