--Coordinates for the Half Pendant of Aquatic Agility is 48,11 off the Coast in Darkshore. I found the V-shaped rock formation (mostly submerged -saw it by swimming just below the surface of the water scanning the seafloor. At the bottom of the V-shaped formation was the chest. I only had to kill one lvl 18 Tresher.
--Half Pendant of Aquatic Endurance is at 21,36. Like the previous post says, go to the Gold Coast Quarry in West fall, then swim out from the coast heading Northeast. Once you get to the edge of the shallows where the cliff drops off, follow that line until you find the big anchor in the dirt. Then go straight down off the side of the cliff and you'll see one of those Bubbly Fissures and the chest is right next to it. Piece of cake!!
--Half Pendant of Aquatic Endurance is at 21,36. Like the previous post says, go to the Gold Coast Quarry in West fall, then swim out from the coast heading Northeast. Once you get to the edge of the shallows where the cliff drops off, follow that line until you find the big anchor in the dirt. Then go straight down off the side of the cliff and you'll see one of those Bubbly Fissures and the chest is right next to it. Piece of cake!!