Vivie,
Wet hair should do nothing to the coil/magnet. What I would be more concerned about is the moisture around the Processor and getting water on the filter for the microphones. Mine last several months before the filter gets hard/plugged and I have to change it out. They are a little pricy in my opinion. When the filter gets plugged, it causes the microphone to receive a muffled sound and I have a hard time understanding speech again. This degredation takes place over several weeks so I don't really know I can't hear as well as I use to. Once I change the filter, bingo, sounds are a lot clearer and I can turn down the volume again.
Good luck. I can say the CI has changed my life. I can hear now almost like when I had good hearing.
Back ground. Started loosing hearing in 2004. December 2006 Implanted with Freedom. Activated January 2007. Sometimes I forget I can't hear and get inconveniently reminded when the battery dies. I have only been caught away from home a couple times without my extra battery when the juice dries out. I have found that by turning off the processor and switching to 900 hz and powering it back on, I can get about 15 minutes more before the processor shuts off again. Gets me through not being able to communicate. For me, at least that is one option.
Good luck.
Steve