Presumably, the kayaker in the video was aware that the massive creature swimming toward him was a harmless basking shark, but the situation must have been unsettling nonetheless. The extremely rare encounter with the planet’s second-largest shark — only the whale shark is larger — occurred off Panama City, Fla. Sightseers and fishermen also witnessed the spectacle. For the sake of perspective, the kayak is 14 feet long. Basking sharks, which can measure 40 feet, feed on plankton and are found in temperate and Arctic waters. Sightings off Florida are very unusual.