We did the half day glacier cruise in Seward last June. Unfortunately, we did not see much wildlife, if at all. Plus, it was very cold outside (in mid-June) and unfortunately we spent a lot of time inside. If you want to do the glacier cruise, go for the half day. I couldn't even imagine spending a whole day in the freezing cold looking for wildlife that doesn't exist. Then again, maybe we just went on a bad day.