Depends what you want to do. I usually just clip it to my swim suit and its fine for sunbathing, soaking your feet, etc... When I plan to swim I disconnect it. If I'll be in the water a long time and its going to get wet I put it in a ziplock baggie and just tape the bag closed. I don't swim with a ziplock bag but for things like white water rafting or kayaking it works well. The pump can get wet but you don't want to dive deep with it or have it underwater for a long period of time. Have fun!

I do not swim, but I'm guessing with the tubing coming out, there would be no way to get a bag completely sealed... so it would leak in water. I almost wonder if it would help to also take an old sock and slip it in, then fold the sock down (so there are 2 or more layers around the pump). That way, the water that does get into the bag would have to be enough to soak the sock before it gets to the pump.