This is solely for the huge jobs update, as there are few divers that will reach 250, but maybe this will spark more incentive once diver is more balanced. These are potential ideas for a 250 perk.
Net - works like a rod, where you cast and after a few seconds, you reel in. This catches 5-6 items per catch. To balance this, the time between casting and getting a bite can be longer.
Bait - only equips to bonus rods, basically lure, where it decreases the time it takes to get a bite. This can also vary, so it's oriented towards a singular item. Such as Cod Bait, Pufferfish Bait, Tropical Fish Bait, etc.
Permanent /waterbreathing. I think a few weeks ago dolphin's grace was suggested. Much more preferred if you also have water-breathing on top of that.