According to the lady I spoke with at Animas (and it wasn't one of the regular technical support people, they got someone else to call me back), it's normal for the inside of the cartridge compartment to get wet with prolonged exposures to water. It's not normal for any other part of the pump (battery compartment, etc.) to get wet, though. The lady also said if the inside of the cartridge compartment gets wet from just brief exposures to water (like showering), that this isn't normal. This doesn't happen for me—it's only swimming for 45-60+ minutes that I notice it.
My pump is under warranty, so she said if I notice the battery compartment getting wet, or the cartridge compartment starts getting wet from brief exposures and/or starts staying wet for days even after drying it out, or I notice any cracks or corrosion, they will replace the pump.
I haven't been swimming in a few weeks due to the holidays, but I'll definitely be keeping an eye on things when I start up again.