Treasure!

You draw up by a small jetty. Tying the boat up with a soggy rope, you step onto the cracked wooden boards. There’s nothing here and you start to get frustrated. Then you notice that the top of one of the posts looks different to the others: cleaner, less weathered. You run your fingers over it and press gently. The top springs up on a hinge and reveals a small recess. Nestled inside is the crystal you have been seeking.