Speak to the Roekillik Elder and he'll tell you he's expecting an offering. You'll be given a recipe for Juicy Fish Roll. You can fish up some Juicy Fish at 1047.89,-290.79,3378.14 . Next, find some umami fungus at 1068.44,-288.57,3350.14 . Grab some salty kelp at 1049.89,-290.71,3367.83 and take it all back to the cook pot near the elder to bake up your offering.
Give your offering to the Elder and then he'll tell you what he knows. Grab some parchment off the nearby table when he asks and he'll draw you a map.