Case in point is a new underwater treasure hunting guide on the ArcheAge Source forums. The info has been translated from a Russian fan site, and it's accompanied by plenty of screens and video (including a map, since this is a proper treasure hunt). The process is pretty involved, and requires a ship, scuba gear, and plenty of air bags to lift chests to the ocean surface.
The guide posits that treasure hunting is more profitable than traditional gathering based on preliminary beta testing, but it also cautions that resource prices may vary quite a bit. Head past the cut for a couple of underwater exploration videos, then head to ArcheAge Source to check out the guide.
[Thanks to Dengar for the tip!]