I have found that AnaLuisa is right on. If I wait to make those Spa appointments for the Sea Days all the time is GONE! And one of the sea days you are in the Glacier, you won't want to miss that.
As for photography, there will be a number of us on the MUSH cruise with all of our camera gear attempting to get those kinds of shots. We'll be doing a few of our own excursions so we can take nothing but photos.