Detonating Bubble

You will never find one in the wild. Duke Fishron makes them, and they only exist for as long as his fight does. He sprays a loose cluster of them at you in his opening stage and lays them down in rings while he spins later on, which is why the back half of that fight wants you flying through the gaps rather than looping around the whole formation.

Each one picks whoever is nearest, flies straight at them, and bursts on contact or once it has covered enough ground. The trap is the hitbox. While it drifts it is smaller than the art suggests, then it snaps out to several times that size at the instant it pops, so skimming past one at the last moment still catches you. A single point of damage kills one, so any weapon with spread wipes a wall of them while you keep moving. Wind drags them sideways too, which means the same volley behaves differently on a windy day and the ones riding the wind close on you much faster than the rest.