Catalyzes the reversible hydration of crotonyl-CoA. Can also use hexenoyl-CoA but not higher analogs. a short-chain (3S)-3-hydroxyacyl-CoA = a short-chain (2E)-enoyl-CoA + H2O Lipid metabolism; butanoate metabolism. Homotetramer. Belongs to the enoyl-CoA hydratase/isomerase family.