What is the sea creature look like a big squid?

Fish, of course.

Answer:

The giant squid is a mollusk of the class Cephalopoda. Cephalopod mollusks such as squid, cuttlefish and octopus are among the most neurologically advanced invertebrates. So along with being big ( the biggest in its class) its also bright.

In case the question applied to other "kind" definitions even though it is a swimming creature kosher rules indicate squid are not considered fish & are not kosher.