Your code is missing the part where you specify what you want selected. "SELECT c.id,curr.name FROM Cargo c, Currency curr" would likely translate to something like:
CriteriaBuilder criteriaBuilder = getEntityManager().getCriteriaBuilder();
CriteriaQuery<Tuple> query= criteriaBuilder.createTupleQuery();
Root<Cargo> cargo= query.from(Cargo.class);
Root<Currency> currency= query.from(Currency.class);
query.multiselect(cargo.get("id"), currency.get("name"));
Query query = em.createQuery(cq);
List<Tuple> results = query.getResultList();
There is an example here using only one table: http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Querying/Criteria#Tuple_Queries