DISCLAIMER: Your Steps and Tasks may be different
Talk to Nydimeth, outside the Haven of Oceanus at loc 15100, 14200, She gives you a note for Branigan. He's inside the Haven of Aerus at 56700, 61000.
Step 1: Seek out Branigan in Haven of Aerus (Aerus Haven), take the Aerus boat from the SW dock at Oceanus Haven to get there
Step 2: Branigan is at the scholar circle there and will send you to find pirate treasure.
Step 3: Dig for some treasures - 10k/53k (in Oceanus Notos also found at loc=9k, 52k), under a rock in a cave, bottom of the ocean, "Rock Cave"~. After digging for about a minute, a red/purple con mob will appear that hits pretty weak and is probably barely soloable by most.
[Another note:At 10k, 53k in Oceanus Notos, you can enter (Region) Rocky Cove while
still on the surface of the water (at least, as of 1.66C). You can also
/DIG while on the surface, revealing a large chest and a splash "above"
you. We actually had to dive down underwater, almost to the ocean floor,
in order to get Luscire Raysanio to attack us for Step 4.]
Step 4: kill the Luscire Raysanio
Step 5: give the chest to Branigen
Step 6: Give the key to Branigen
Step 8: return to Nydimeth, get your boots.