Leeches belong to the phylum Annelida. They are worm-like parasitic animals. they feed on blood of other animals. Blood feeding animals are called sanguivores. Crocodiles are reptiles. Both Crocodiles and leeches are able to live in water. Leeches stick to the body of crocodiles and suck blood to feed themselves. Thus, relationship between leech and crocodile is a parasitic.