Monster Hunting

Put 4 Freshwater Pike Heads into the Empty Fisherman's Box. Dive into the lake and put the box down by the big snag on the bottom, between the bathhouse and the Waterfolk village. Wait for the lake monster to appear and kill it. Take the monster's head to Soti the Stinky.

Hey, there. Wait a second.
Why are you making a face? Yes, I smell, but I'm a fisherman. So I smell... like fish. That's the job.
It hurts... It also hurts that they are calling me a liar. I'm the only one who's seen the lake monster!
But it does exist! I saw it! It's huge! I call it Fangy 'cause it's got so many teeth.
I've only ever seen it when I'm fishing. It never shows up if you just sit on the shore and stare at the water. If you wanna fulfill my request, you've got to become a fisherman yourself.
Kill four fish and put their heads in this basket. Then place the basket in the water near the Waterfolk tribe, just to the south of the island. That's how we'll lure the monster out! At that point, it's all yours to deal with.
I must warn you, it's a horrible and evil beast.If you do manage to kill it, bring me the monster's head. Let them see that Soti the Stinky ain't some kind of windbag. He's an honest fisherman!