Huzzah and behold! I finally got round to doing a mock-up of how I wan't the fishing minigame to look:
Each dungeon will have Skell's Fishing Hole in it, tucked away where only the most daring and inquisitive adventurer can find it! In the minigame you get rewarded for the fish you catch, and if you hook the mystery box at the bottom of the pool you get an even better reward! But you only have a limited amount of hooks, and old Skell is tight when it comes to giving new ones so you'll have to be careful!