Bajo Alcyone

1. J
2. F
3. M
4. A
5. M
6. J
7. J
8. A
9. S
10. O
11. N
12. D

Bajo Alcyone is a submerged seamount off Cocos Island, Costa Rica — discovered and named by Jacques Cousteau and his crew during expeditions aboard their 1985 turbosail research vessel Alcyone. Cocos is liveaboard-only via a 32–36 hour crossing (~550 km / 342 mi from Puntarenas) and was inscribed as a UNESCO World Heritage Site in 1997 (extended in 2002 to include the surrounding marine area). Alcyone tops out at ~25 m and drops to 40+ m; it is famous for what are consistently described as the largest scalloped hammerhead schools in the world, particularly Jun–Nov when cooler upwelling water arrives. Galapagos sharks, silky sharks, whale sharks, marble rays, and tiger sharks all rotate through. Strong, unpredictable current; reef hook standard. Park permits and ranger fees mandatory; only a handful of liveaboards operate.