ajkula

1. shark
   Na toj plaži su videli ajkulu. — They saw a shark on that beach.
   Deca vole dokumentarce o ajkulama. — Kids love documentaries about sharks.
2. colloq. (of a person) shark
   On je prava ajkula u biznisu. — He's a real shark in business.

In Serbia the usual word is ajkula. Morski pas is understood but is characteristic chiefly of Croatian and coastal usage.