Kenny 2x4

Best answer as chosen by Asker / Ratings
You need to get to the "end" of the level first. When you do, on one side there is a set of stairs going down to the bonus level, and opposite that there is a cannon that points toward and ice berg.
From there, destroy it and glide to the whirligig and you'll end up on the ledge outside the sort of shelter that has the ice with the crack in the middle. Find the overhanging edge into the shelter and then do Spyro's "vertical headbutt" over the crack to swim under the ice to the gems.