AFKFishing or "The plugin" was made by me for my friend who wanted the 'old' fishing logic back from pre-1.16. The plugin works instantly after being added to the plugin folder. No initial configuration is required unless you wish to specify custom probabilities for the various categories. See 'Configuration'.
To clarify; this does alter every loot you get from fishing (not when you reel in a player or a dropped item though!). It does not matter if you are at open seas or at an old* AFK fishing farm. It will randomize the loot you get from fishing.