He asks you to deliver a message to a mining operation on a nearby island - the small isle to the west. Swim over and the ramp up is at 1586,-233,-1474 . When you approach the island you'll get an update and your task changes to rescuing the miners from the sirens.
There are several encounters of solo sirens on this island, they are level 58-59. Once they are killed An Auroral Selkie will spawn. Kill her and return to Siraj to complete the quest.