If you've ever floated over the rocks near Playa Mantas and seen a little yellow-and-silver fish with bold black stripes zip past, you've met a sergeant major. They're one of the most common — and friendliest-looking — fish on a snorkel tour near Jacó, and they're a perfect first fish to learn to recognize.

How to recognize a sergeant major

The sergeant major is easy to pick out thanks to its five bold black bars running down a silvery-yellow body — the stripes that give it a military name. They're small, usually palm-sized, and they move in loose groups rather than alone. That combination of bright color, strong pattern, and safety-in-numbers makes them one of the first fish new snorkelers spot and remember.

Busy little reef residents

Sergeant majors are always on the move, darting around the rocks to pick at algae and tiny bits of food drifting in the current. They're curious and not easily spooked, so they'll often carry on feeding just a few feet away while you float and watch. That boldness is exactly why they're such a treat for kids and first-timers — you don't have to go looking for them, they come to you.

Where you'll see them in our cove

Sergeant majors love the shallow, rocky edges where algae grows — which is exactly the calm water we snorkel near Playa Mantas. You won't need to swim far or dive deep; they work the same stretches of rock near the surface, and your in-water guide knows where the groups gather. Clear morning water is the best time to catch their stripes at their sharpest.

Look, don't touch

Sergeant majors are curious and gentle — the best way to enjoy them is to float quietly and let them come to you. There's never any need to chase or touch reef life. Our guides keep everyone a respectful distance so the cove stays healthy for the next group.

The sergeant major is just one of many characters down there. For the full cast, read our guide to the fish and marine life you'll see snorkeling near Jacó, or see real guest photos and reviews on the Snorkel Jaco reviews.