Guessing game

I am large. My skin is gray. I have a long nose. What am I?

I live in Africa. I have brown/golden fur, four legs, and very sharp teeth. My hair is long and wild, and I can roar!

I have no arms or legs, but my tongue is very long. I have a long, skinny body. I like to hide in the grass. What am I?

I can swim. I am a bird.

I live in a river. People think I'm scary. I have green scales, a long face, a long tail, and very sharp teeth. What am I?

I live in the ocean. I have a big mouth full of sharp teeth. People are scared of me. What am I?