And yes, it's not a joke, there is a species of sharks that eat plants, and it is the tiburo hammerhead shark. It has just been discovered ,by a team of American researchers from the University of California and Florida International University.
Unlike its congeners, heavy consumers of meat, Sphyrna tiburo or hammerhead shark Tiburo loves plants and is especially able to digest them. 62% of its stomach may contain turtle grass (Thalassia testudinum), a plant species. To study this phenomenon and better understand it, scientists placed some young sharks in a saltwater pool and fed them with seaweed for 3 weeks. This vegetarian diet had no impact on their growth which continued harmoniously. Their diet consisted of 90 plants and 10% crustaceans and small fish. Scientists have found that 58.6% of organic matter in plants is digested by sharks, thanks to β-glucosidase, an enzyme that can degrade cellulose. The hammerhead shark tiburo is an omnivorous shark unlike other species.