There must be a speargun technique with this, but I'm having no luck finding it. Equipping the speargun or a fungus spear, hunting spear, or oily spear doesn't give me the option to use it or any of the other things to load a spear into the speargun. Hunting the fish in the Great Stand of Seaweed with the speargun equipped also doesn't yield a technique, although it does let you catch some fish. Just plain old fighting underwater with a ranged deck and the speargun equipped gives amusing messages about how ranged weapons don't work well underwater but no new technique. Any ideas on where to get special spears to load into the speargun or otherwise learn a speargun technique?
(I'm interested in finding this hypothetical technique mostly just for because it looks like it's there to spade. Unless the technique is absolutely devastating, or there are multiple speargun techniques for different chain numbers, it's hard to see a weapon that gives +4 Ranged Power and +4 Stealth Power competing with a hunting spear or other melee weapon, especially with ranged techniques in general not working well underwater.)
Should we maybe make a special page for underwater adventuring with a list of how it affects walk away and all the various techniques and whatnot? That information is scattered over individual technique pages and diving ability and the like, but it might be nice to have it all together in one central location.