Ques. for school children

Thanks for the comment about the school kids following. Here is a special post for them.

Can you tell me what type of fish this is? I took this picture in the lagoon on Rarotonga in the Cook Islands.

In a Papeete post, what sea animal is in the 4th picture? What is it's name and is it poisonous or dangerous? I took this picture while snorkeling on a beach in Moorea.

Thanks!