When in the area on the way to the mockturtle there is a Hobby Horse ice patch that appears to be unbreakable. You cannot break it from the "top". Go back outside before going to the Bottled Ship. Notice that there is a small pond of water that goes into the ice on the cliff at the bottom (where a spring mushroom is located). Use your Shrink Sense to find an invisible platform that will begin moving into the ice and allows access to a secret area. To exit the area use the other spring mushroom to catapult yourself through the unbreakable hobby horse ice patch.