San Andrés Archipelago

The San Andrés, Providencia and Santa Catalina Archipelago sits in the southwestern Caribbean, 750 km northwest of the Colombian mainland and 230 km east of Nicaragua. Colombia's sovereignty over the islands was reaffirmed at independence, though Nicaragua has contested it and the International Court of Justice trimmed the maritime boundary in 2012. The UNESCO Seaflower Biosphere Reserve covers the entire archipelago, including the reef systems surrounding Providencia (Old Providence) and the atolls of Roncador, Quitasueño, and Serrana. San Andrés island itself is denser and more commercial — a free-port economy, substantial resident population, and tourist infrastructure built around the extraordinary colour gradients of the shallow reef flat dubbed the Sea of Seven Colours. Providencia, two hours north by small aircraft or fast boat, is dramatically less developed and ecologically intact. The tidal regime throughout the archipelago is oceanic Caribbean microtidal — spring range 0.3 to 0.4 m, weather and wind dominant. Predictions come from Open-Meteo Marine, accuracy class ±45 min / ±0.2–0.3 m.