Yes the water will be cold, not much warmer than 40°, and so will you if you go snorkling in a wet suit. The only way to stay warm and enjoy activities in cold water is in a drysuit, and they are fairly expensive. If the marine life is anything like that in Washington state, there is no coral, but plent of other life, fish, invertibrates and even mammals. As much as I like diving, even in cold water, I think I'd skip the Alaska Snorkling.
Or are you joking about the Alaska snorkling excursion?