Sea unicorns are a rare species of seahorse with a large horn on their foreheads. Whenever they appear, they are usually seen with rainbows, flowers, and other kind-hearted imagery.
Sea unicorns are white seahorses with periwinkle fins, tails, and a golden horn.
A sea unicorn appears on a $20 wall hanger in "Bossy Boots" in Mr. Krabs' office. However, it resembles a regular seahorse more than a sea unicorn.
When SpongeBob sings the song "Down the Well" in "Wishing You Well," a sea unicorn appears when SpongeBob sings, "Although every day the pain grows, you'll ride unicorns on rainbows, if you throw all your dreams down the well."
They are also seen in the background on the ball toss game in "Company Picnic."