bigdog

This time of year is not a good time of year for bananas to be sitting in water, but being in Cal doesn't hurt. It's cold and wet that will do a banana in. The roots do need oxygen though, or the plant will eventually die. It would have to be submerged for a pretty long time for that to happen though.

On a side note, one species that is supposedly extremely tolerant of water-logged soils is Musa itinerans.