You knock on the door of the seaside shack, but there's no answer. Maybe try back later.
First visit at level 11 or higher:
Hello there, young Adventurer. Back when I was your age, I used to be quite a fisherman. These days, well, what with my arthritis, and my gout, and this old war injury, well, I don't get out there so much anymore.
Say, is that a set of SCUBA gear you've got there? Maybe you can help me. I lost my favorite boot, you see. Dropped it right off the side of my boat. Time was I'd just fish until I dredged it back up, and boy, lemme tell you, was it a hoot! But not anymore. That dang marlin sapped the last of my strength.
Think you could go down there and get it for me? I'd be obliged, yessirree.
Oh, and hey, if you wanna take your little buddy with you, this'll help.
You're going to need something to help you breather[sic] underwater. Normally, I'd just sell you an old SCUBA tank, but I'd like you go down there and evict the Naughty Sorceress, so have my best pants.
If you need something to help you breathe underwater, I've got this old SCUBA tank I'd be willing to part with. Let's call it 10,000 Meat. On second thoughts, let's call it a SCUBA tank, and say it costs 10,000 Meat.