Ok, I found the proper are where the Siren coercer spawns. Along with the listed location, there are 3 more coercer's that can spawn in the same area.
@ location -556 ,-313, -41 drops the Gllomwater Bow
@ location -479, -313, -46 drops the Cloak of the Seacaller
@ location -582, -255, -27 drops the Sleeves of the Kelpmaidens