Blowey is a tiny orange fish, which inflates much like a pufferfish, and the fifth enemy you you will encounter. Though they are the least of your worries (unless a future update makes them deadlier somehow) and currently only appear in the Forbidden Bayou, most likely since it has water hazards.
They are the sole enemies thus far to have a singular sex grapple (which happen to be the reason for their namesake). They're not even the biggest threat, as you'll take damage from the water they swim in more often than their actual attack.
When you leap over them, or stand too close to the water's edge, a small warning sign will pop up. If you're in this spot when they leap, you'll be grappled. They can't be punched or seduced, but are pretty easy to avoid with basic platforming jumps.
As of Version 0.14.104, Bloweys are slightly more dangerous as they can now leap through old and broken platforms found in the Forbidden Bayou.