From the introduction: This short encounter is set in a cave carved by tide on one side and a freshwater stream on the other. Its elevation is between the high and low tide levels. When the tide goes out, water surges north through the cave into the ocean. When the tide comes in, water surges south towards a small lagoon. The cave is filled with poisonous coral, and crabs. The crabs eat fish that are washed in by the tide and poisoned by the coral. Abundant and easy food as made them large, numerous and aggressive. PCs that need to get through will face powerful tidal surges that will constantly threaten to sweep them from their feet and into the poisonous coral. They must deal with the crabs while successfully navigating these challenges. User summary: An adventure for three to five 1st - 2nd level characters