The spot-fin porcupinefish is circumtropical:
Diodon hystrix may be up to 91 cm long and weigh as much as 2.8 kg. It is coloured tan with dark spots above and pale below, and has many long, moveable spines. It is largely nocturnal.
Juveniles are pelagic up to the time that they are about 20 cm in length. Adults favour lagoons and seaward reefs, sheltering under ledges or in caves during the day. Although classified as benthic, they may sometimes be found hovering high in the water.
Diodon hystrix are poisonous to eat, possibly due to the accumulation of tetrodotoxin.