Seas are stewing off Maamigili, the southernmost island in Ari Atoll, one of 26 natural atolls in the 1,190-island Maldives archipelago, which rests upon a vast underwater mountain range in the Indian Ocean, southwest of India. Our excursion craft, a traditional wooden Maldivian dhoni, rocks like a caffeinated cradle alongside our main vessel, 128-foot M/V Four Seasons Explorer, making transfers between the two to be undertaken with care. This morning’s adventure is worth weathering waves, though. We’re setting out to look for the planet’s biggest fish, the magnificent, vulnerable whale shark (Rhincodon typus), which cruises the atoll’s outer edge year-round. This U-shaped, 4,863-hectare South Ari Atoll marine-protected area (MPA) is the largest in the Maldives, extending from Rangali Island in the west, around Maamigili to the south, to Dhigurah Island…