Use the map to travel to the docks and then proceed to port. Pick up the water platypus egg from below the ramp and return to the docks. Enter the trawler and take the bait from the bin. Talk to the fisherman and show him the razorfish (the one taken from the tavern during the quest for air platypus). Tell him that you've fishope it using special bait. Show the fisherman the bait, and he will fish out a goliath tigerfish. Unfortunately, the fish will escape and return back to water.
Travel to the market, approach the apothecary and dig out overdue pills from the trash. Place the pills into a bait bucket found next to the fisherman. Show the fisherman the bait again and pick up the goliath tigerfish.
Use the map to travel to the industrial district. Enter the door leading to the Doc's workshop and use the goliath on the bucket with paint. Put the egg into the fish's mouth. Enter the antechamber (on the right) and resurrect your fish using the electrodes. Now, proceed to Bellevue. Along the way, the frankenfish will start to shiver - keep it alive using the water (the glass of water taken from the Poet while on the quest to acquire air platypus). Use the map to travel to Bellevue, enter the Seagull's house and place the fish in the aquarium. If you do not complete the action fast enough, you'll need to return to the Doc's workshop and repeat the procedure by clicking on the electrodes. Pick up the water platypus from the aquarium and place it in the nest at the port (on the top of the pole)