Tired as I am, I'm still finding progress on my character to be fairly smooth.  As long as I don't push it, he should come together well.

On the earlier ideas.  These are my thoughts.

I agree with the general range of options and variety available.  However, there's a couple things that I wanted to bring up that came to mind.

- With less large scale fishing per ocean area, the fish population will have exploded and super schools with millions of fish could easily be a thing.

- Larger fish could likely be more comfortable closer to the surface than previously known as well as being far more numerous.

- Glaciers and partially flooded caverns, sub-oceanic ones, could also make for discovery events that spark interest.  Glaciers would be a source of isolated and preserved fresh water, high quality at that.  Partially flooded cave systems could be home to species of crustacean that are difficult to find with current technology in the open ocean due to their preferred depth.  Also, crabs would have returned to their pre-harvesting sizes.  That means full scale king crab.

- The possibility also exists for illegal slave traders who execute swift night raids on settlements and slip away in the night to sell their catch elsewhere.  (This would tie into my prospective character's backstory, if I manage to get organized enough to officially join.)

- Also, shark leather armor would be fairly common among those who work in rougher occupations.  The tiny teeth on the outer surface would discourage creatures from latching on and the toughness of the leather would make for decent armor anyway, especially if it's backed with layers of something thinner and cheaper.

- I recommend, as a starting scene, having everyone in the docks on a day when more business is done than usual.  The business justifies their presence while also getting everyone in sight of the harbor for the arrival of something notable, a ship of some kind that usually means something important.  Possibly a ship flying the flag of a known group of famous cartographers and explorers.  This provides factors that unify the scene and keep all the characters thinking about the same general kinds of things.  It could also be used to spark conversation and further plot development.