This necklace is made of a thick silver chain and a pendant that is gold and is styled after an anchor. It is very light despite the size. It's obvious that this pendant was crafted by surface dwellers simply by the astetic design with it being very human . The pendant is solid gold, and has an inscription that says, "Sink or swim son, we are proud of you." On the back.
This necklace allows the wearer to add 20 feet to their swimming speed when moving along a vertical axis when the command words are spoken/communicated to the amulet. "Sink" increases the weight allowing you to sink faster. "Swim" lightens the amulet allowing you to rise in the water faster.
Still trying to come up with more aquatic based stuff. Enjoy!