As the characters reach the end of the tunnel, they can see a cirlce of water apparently floating on the ceiling. On closer inspection they find that it is actually an opening up into an ocean. Looknig into it, the water is a pure crystal blue, tropical fish can be seen swimming through the reefs and among them, are a group of Merfolk. If the characters do enter the water, they will see a pristine coral reef, with a kelp forest in the background. As they follow the merfolk back to their city, they will be able to see an island taking up the center of the lagoon.
The city is a large grouping of underwater caves that have been adapted to be homes. The homes are roomy and well furnished, containing everything that could be needed. Where the caves simply left something to be desired, coral was grown to fill in the gaps. In fact, the town hall, the only non-subterranian building is made of living coral.
The kelp forest extends the entire length of the lagoon and actually has been grown to make a barrier between the entrance to the ocean and the city. The merfolk down does have defences, they are there to ward off any predators that might come in from the ocean. The kelp forest is the last defense, but a good one, most large creatures avoid kelp so as not to be tangled and drowned.
In front of the kelp are jagged rocks seperated from the forest by an open field of sand. The rocks have all been placed fairly close together, thus limiting the size of creature that could make it to the city. Before the rocks though are the gates, made completely of Mother of Pearl. They are generally left open, although are closed during certain times of the year when sharks are more prevalent.