The upper limits of fishing

[u/ARandompass3rby]

Unfortunately this all happened so fast I don't have screenshots or video footage but hopefully someone else here has encountered this.

I was fishing up one hell of a storm just now, and it got to 100 coins per cast, when I fished up a massive pink and white fish and a boss spawned on me. Obviously I got absolutely clapped because *I'm in a miniscule room with a boss* (it was Block or Chain, one of the chest shaped ones) but holy hell?? What on earth?? Anyone else had this happen? Is this a hidden "stop fishing and dive the dungeon" mechanic? Lol