Phase 1: Tentacles
Barinade is attached to the ceiling and floor by tentacles. First, use your Boomerang to cut the tentacles connecting it to the ceiling. Then, use the Boomerang to cut the tentacles connecting it to the floor. This will free Barinade to move around.
Phase 2: Core Attack
Once free, Barinade will spin rapidly, surrounded by electric jellyfish. Use your Boomerang to stun Barinade's core. While it's stunned, run in and attack the core with your Kokiri Sword. Avoid the electric jellyfish and its spinning attacks. Repeat until defeated.