Rsgoldfast - Inform Gompar you fixed the wall
To repair the wall, then you must have a hammer, 23 Gomrock Bars (could be purchased at Mogrin in any area or RuneScape gold mined outside with 43 mining and smelted in an underwater port, maybe not a furnace, together with level 51 smithing) and level 37 construction. Repair the wall. Go back around Captain Murk and tell him to sail a little further away so that you can dive. He will do that. Proceed to the palace (can be entered through some region) and speak to Gompar.
Inform Gompar you fixed the wall. He'll thank you and supply you 16,000 gp. Tell him you believe the boat belonged to a priest that was sailing such a way. He will say he watched a couple human beings swim to a nearby cave at a water cliff but it caved in because of a little earthquake. Go in the cave and it will be dry in there since the water can not reach far enough to flood it. Talk to Captain Lockbard and he will thank you for finding him. He'll give 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 bringing the 3 individuals up to the boat with the assistance of this Breathing Orb. Congratulations, quest complete!
To get fish pets you have to have level 73 summoning. Find fish eggs in submerged caves or someplace, (should have level 73 summoning) if you discover a shark pup, then you are very fortunate. If you take more than 1 egg you can just get 1 fish. Go to the Fish Tamer's room of the palace and he will have a fish egg incubator (you can't incubate any additional egg than a fish egg in there.)
Set the egg in it and wait till you have a fish (you can not place the shark puppy in it.) They help you catch fish underwater quicker depending on the stage. Stages are pup (there isn't shark eggs), juvenile afterward mature. The next is the Angler Fish. It is the only resource for lighting in dark underwater cave, as candles or lanterns would go out. They have three phases, egg, larvae and then adult.
Pufferfish are the next. Their eggs are located on the surface of the water that you can get from scaling up the anchor rope. Climb it up again to visit Captain Murk. Get a pufferfish egg and then incubate it. It will hatch soon. The most common fish would be the salmon. They allow you to buy OSRS gold find eggs. Whenever you are in 10 squares of eggs, it will swim in circles.