Sponge lure and rod
Take the Crab Carcass bait from its mini island and fish it on the long Fishing Rod; Sponge bites on 8.8% of casts, the same as Starfish.
Sail away and find a fresh islet to restock the bait.
Drip Sponge
Drip Sponge exists and rolls the base 10% (25% with the full Wishbone).
Expect about 114 bites per drip Sponge, 45 with the Wishbone.
Sponge sell price
Sponge sells for €4.