A Link to the PastDark Palace. They don't make natural appearances, but rather, they appear after Link has defeated a Red Bari. If Link strikes the Red Bari with his Master Sword or a number of basic attacks, the Red Bari will split into two smaller Biris.
Biris have almost all of the same attributes as their larger Bari brothers. They resemble that of floating jellyfish, with their bodies continuously bouncing around. They will occasionally give off an electric shock, harming Link if he comes into contact. If Link comes into contact with a Biri, a full heart of damage will be done. If Like tries to slash at a Biri while it is electrified, again, a full heart of damage will be done.
Link can easily defeat these enemies from a distance using a number of projectile weapons. The Beam Blade from Link's Master Sword will defeat a Biri with one shot. Alternatively, Link can get rid of these foes with the Hookshot.
Ocarina of Time
These floating jellyfish will shock you immediately upon contact and while they can be killed with your Sword, it'll also hurt you. To kill them, the player must use Deku Nuts which then stun the jellyfish, allowing the player's sword to cause damage either through a simple strike or a quick Spin Attack. Once the player has the Boomerang, he/she can use that to easily kill them in a single hit. In general though, it is best to simply avoid them altogether.
Oracle of Ages
Electrified Biri from A Link to the Past.