All Points Island is where Mermaids and Humans live together in harmony. People live on land, and mermaids in water. The Windsnaps were a slightly unique case, because they were a couple of a human and a Merman, and they had a daughter who was both. They lived in a half-sunken boat, that had been remodled on the inside to be a modern house. The top half was designed for people, and then trap doors were all around the house/boat that lead to the lower half, which was designed for merfolk. The trap doors made it easy for the family to converse with each other, and for Emily to reach her Father's way of living.
the lagoon is in the south east corner of the island. It is a lovely place with tropical plants and flamingoes. However, people and merfolk were cationed never to enter, for just past the lagoon, lay the Kraken's cave, where it slumbers.