Decoder #8
When you visit the Dock Colony for the first time, a woman in front of the clinic tells you of a Fish Detector that her husband lost. Go to the Kukai Foundation's cleaning place and inspect the tuxedo to find the Fish Detector. Talk to the girl in the Iron Man bar, sitting at the lower left table. She says that she lost an important ring and asks you to find it. Go to the Private Beach and go in the water where the fish show up on the radar screen. Run up to every fish and press Circle. Sometimes you will get an item, and sometimes you will not. You can get a Med Kit, a Speed Stim, and the Engagement Ring. If you return to the beach on any return trips, the Med Kit, and Speed Stim will be there again. Give the ring back to the girl in the bar. She will give you the Decoder #8 to open the red door.