While Puerto Rico has hundreds of islands and cayos, listed below are the most popular offshore islands and cayos for visitors, ranked according to prominence in travel guides, boat-tour itineraries, and day-trip reviews. The three inhabited islands (main island, Vieques, Culebra) are excluded here since they are already well known; this list highlights their smaller satellite islands and other offshore destinations. You can reach these with your own private boat, a private charter, or a group tour.
| Rank | Island / Cayo | Where | Why It’s Popular | |
| 1 | Culebrita |  |
Culebra | Culebra’s most iconic satellite cay, reachable only by boat; famous for its 19th-century lighthouse ruins, the tide pools known as “Jacuzzis,” and Playa Tortuga, a protected sea-turtle nesting beach. |
| 2 | Cayo Icacos |  |
Fajardo | An uninhabited, powder-white-sand island inside the La Cordillera reef system; the single most popular stop for Fajardo catamaran/snorkel tours thanks to calm turquoise water and coral just offshore. |
| 3 | Isla Palominos |  |
Fajardo | A private-feeling beach destination tied to the El Conquistador resort, sold as an all-inclusive catamaran day-cruise stop with kayaking, hammocks, and snorkeling. |
| 4 | Cayo Aurora |  |
Guánica | A mangrove-fringed islet reached by a short public ferry from Guánica, beloved for its calm swimming lagoon, snorkeling reef, and mangrove tunnel kayaking. Known by locals as “Gilligan’s Island”. |
| 5 | Isla Caja de Muertos |  |
Ponce | A protected nature reserve accessible via passenger ferry/kayak tours from Ponce, drawing visitors for its 1887 lighthouse, hiking trails, and clear snorkeling waters. |
| 6 | Cayo de Luis Peña |  |
Culebra | A nature reserve islet just off Culebra popular for hiking, quieter/less-crowded snorkeling than Flamenco Beach, and kayak excursions. |
| 7 | Isla Desecheo |  |
Mayagüez | A dramatic, cliff-ringed uninhabited island and National Wildlife Refuge famed among divers for exceptionally clear water, walls, and marine life just off Rincón. |
| 8 | Isla de Mona |  |
Mayagüez | Nicknamed the “Galápagos of the Caribbean,” a remote nature reserve with giant iguanas, sea caves, towering cliffs, and world-class scuba diving, reached by multi-day boat expeditions/camping trips. |
| 9 | Cayo Santiago |  |
Humacao | A famous rhesus-macaque research colony off Punta Santiago; landing is prohibited, but kayak and boat tours circle it to view the free-ranging monkeys, making it one of the most-searched offshore attractions. Referred to as “Monkey Island” by locals. |
| 10 | Isla Magueyes |  |
Lajas | Home to a University of Puerto Rico marine research station and colonies of iguanas; serves as the gateway/launch point for La Parguera’s famous bioluminescent bay boat tours. |
| 11 | Cayo Caracoles |  |
Lajas | The single most-visited cay in the La Parguera archipelago, known for a shallow sandbar, lively weekend boat atmosphere, and easy snorkeling just offshore. |