Bring good armor and a healthy tame, the fish can dish out alot of damage and standing next to one for only a second could mean death, the fish have a low aggro radius so leading them can be tedious. Once you have successfully made the fish follow the turtle (the fish will stick very close to the turtles butt) have one person on foot follow the turtle around and another on a bary farther away to kill sharks. Side note all turtles tame at the same rate regardless of the lvl from what I've seen.

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