Tell Gompar you mended the wall. He'll thank you and give you 16,000 gp. Tell him you believe the ship belonged to a priest that was sailing this way. He'll state that he watched a few human beings float to a nearby cave at a water cliff but it caved in because of a small earthquake.
Proceed to the cave and mine the rocks blocking it (requires 43 mining.) Go in the cave and it'll be dry in there since the water can't reach far enough to flood it. Speak to Captain Lockbard and he will thank you for finding him. He'll provide you 3 classic lamps he discovered in the cave. (Rub them for 10,000 XP in almost any ability.) A cutscene will occur showing you attracting the 3 individuals up to the ship with the help of the Breathing Orb. Congratulations, pursuit complete!
To find fish pets you have to have level 73 summoning. Find fish eggs in underwater caves or elsewhere, (must have level 73 summoning) if you find a shark pup, then you are very fortunate. If you take more than one egg you can just get one fish. Go to the Fish Tamer's area of the palace and he'll have a fish egg incubator (you can not incubate any other egg compared to the fish egg in there.)
Put the egg inside and wait until you've got a fish (you can not place the shark pup in it.) They help you catch fish underwater quicker based on the point. Stages are pup (there is not shark eggs), juvenile then adult. The next is that the Angler Fish. It's the only resource for light in dark underwater cave, as candles or lanterns would obviously go out. They have three phases, egg, larvae and adult.
Pufferfish will be the next. Their eggs are found on the surface of the water which you can get from scaling up the anchor . Climb up it to go to Captain Murk. Get a pufferfish egg and then incubate it. It will hatch soon. They blow up when an enemy strikes youpersonally, poisoning the enemy. The most common fish is the salmon. They allow you to find eggs. When you're in 10 squares of eggs, then it will swim in circles.