A:AnswerAdvertised as "WATER RESISTANT" and shows can be used while SWIMMING, I wear mine in the SHOWER with no problems, but have not tried SWIMMING. I suspect since your arms would be in and out of the water, SWIMMING may be ok. Would not try SCUBA DIVING, or SUBMERGING in water for a long period of time. May get a better answer at the FIT BIT HELP CENTER or COMMUNITY MESSAGE BOARD.