Calling ocean creatures alien is wrong. They aren't alien. The interest in space travel is simple to me. We can possibly learn about real aliens. We can also ensure humanities survival even in the event that the Earth is completely gone. Studying the ocean is just mostly about learning some semi interesting biology and mostly boring geology.
They are alien in that they are adapted to a totally different environment to us. But not alien in that they are a branch off the same tree of life as we are.
If you are interested in finding out more about octopus evolution and intelligence I recommend: " Other Minds: The Octopus and the Evolution of Intelligent Life" by Peter Godfrey-Smith.
"My octopus teacher" on Netflix is also well worth a watch.
Other humans are aliens. It is all a matter of degree. Octopods are about as alien an intelligence as we have on Earth. It is easy to imagine less-alien outsider aliens
"X is just mostly..." is a reliable way to begin a falsehood.
