Talk completely to DeCava. He will tell you what he wants done.
This is a 2-parter puzzle:
1. To understand manatee.
2. To learn how to sound manatee.
To understand manatee - you already did several things for that puzzle - the locket.
Remember what DeCava stated - someone at Flotsam taught Santini how to understand Manatee.
HINT: - You as Guybrush has to go to Flotsam.
HINT 2: - What did just happen to DeCava when you played with the locket.
-I thought this was the funniest part of the game.
Remember that the arrow of the locket transfers that person to the other picture you point it to. Place picture of Guybrush over DeCava's.
Turn the locket arrow to point to Voodoo Lady
To sound like manatee:
You already know that you need the Tongue of the Manatee and
one of the crew knows.
You already interrogated them.
At the helm is the file of the pirates - it is beside the barrel with the locket - study what's inside.
Then interrogate them again.
Bugeye will cave in.
Noogie will cave in with facial expressions: stinky, crosseyed and geezer.
Moose then knows where it is. Now that you lopped the head of Santini - he will be scared - interrogate him now.