Balloonfish: Big Eyes, Long Spines, and a Party Trick

The balloonfish is a porcupinefish — a round, big-eyed fish covered in spines that normally lie flat, but stand straight out when it inflates into a prickly ball. Gentle and curious, it's a snorkeler's favorite. Here's how to spot one snorkeling near Jacó, plus five fun facts.

Balloonfish · Diodon holocanthus

How to spot the balloonfish near Jacó

Look under ledges and in shaded reef nooks for a plump, tan-and-spotted fish with oversized eyes and spines lying flat along its body. The balloonfish often rests quietly by day, drifting out at dusk. Admire it from a respectful distance — never chase it, as forcing it to puff up is stressful and harmful.

5 fun facts about the balloonfish

• It inflates into a ball. When threatened it gulps water to swell into a round, spiny balloon far too big and prickly for most predators to swallow.
• Spines that stand on guard. Its spines lie flat most of the time, then point straight out as it inflates, turning the fish into a floating pincushion.
• Headlight eyes. Large eyes help it hunt at dusk and night, when it comes out to crunch snails, crabs, and hermit crabs.
• A crushing beak. Fused teeth form a powerful beak strong enough to crack hard shells that defeat most other fish.
• Please let it stay calm. Puffing up is a last-ditch defense that stresses the fish, so a good snorkeler watches quietly and never provokes it.

The balloonfish is just one of many characters down there. See the whole cast in our Snorkel Jaco fish directory, or read real guest photos and reviews on the Snorkel Jaco reviews.