Walk to the Gap blowhole, between First and Second Beach, at high tide (but stay well away from the shore because of dangerous waves). Another great natural site that can be accessed on foot is Bulolo Waterfall, which requires a rather strenuous 90-minute walk to get there. For the waterfall, you'll need a guide – contact your accommodation. An easier walk goes from Second Beach to Third Beach along the coastline; you don't really need a guide, but if you're on your own it's safer to take one.