Sailfin tang

As their name suggests, these fish are extremely tall thanks to their large dorsal and anal fins. Young fish of this species swim with their fins spread out, but once they mature they swim with a more closed posture. When they are surprised or trying to appear intimidating, they will spread out their fins as wide as they can.

Scientific Name
Zebrasoma veliferum
Order: Perciformes, Family: Acanthuridae
South of Sagami Bay, Pacific Ocean