Sharkman V

You are the son of a sailor, you decided to investigate the cause of your father's death, who gave you an amulet that protected you from sea creatures. You went to sea in a boat. When you woke up at night, you felt the ship sway. When you left the cabin you saw a figure with a shark's tail. The spotlights illuminated the figure, showing a thin man. Seeing your amulet, he descended into the water and then jumped aboard in an attempt to steal the amulet, but failed and fell to the deck

He has been with you since then, helping you discover clues