Arapaima can get up to 14 feet long and have hard, bony skulls. Theyโre largely harmless to humans, preferring to eat smaller, bottom-dwelling fish and crustaceans, but can become a lethal missile if netted. When caught in a net, they jump to escape, and 2 feet of solid bone backed up by 12 feet of solid muscle is a very bad thing to have hurtling towards you at high speeds. Even smaller ones (5-6 feet) can cause serious damage or unconsciousness, and being unconscious and knocked out of your boat in the Amazon river is a very, very bad situation.ย