I think rockets have this unmatched spectacle, especially for those born in a certain time. Submarine exploration is really cool, but I don't imagine the launching of a new submarine explorer is going to match the momentous-ness of the launch of a new rocket.

There's also just a kind of social narrative issue, where space is cool because sci-fi and aliens and astrophysics, while the deep oceans are scary because dark and unknown and shipwrecks. I guess it's like "if we explore space, we might find alien life; if we explore the oceans, we might find a really weird fish".

There are economic and political incentives to build rockets and space infrastructure.

Less so for submarines exploring the depths of the ocean, even if the latter is equally or more interesting from a scientific exploration perspective.

Well going into space has clear advantages for our species. Firstly, it provides a backup in case something happens to earth, like if it gets hit by an asteroid. It could also potentially be untouched by a nasty war on earth, but odds are it would get dragged into it. Secondly there are commercial possibilities like mining in space, or space real estate . Thirdly, astronomy is one of two ways we expand our knowledge of physics (the other being particle accelerators), and new physics can lead to good things down the line.

There are benefits of exploring the oceans too, like maybe finding some missing link species and learning about biology maybe some geology. But they seem much lesser to me.

Because it is not about science.

Totally agree. While space exploration is an exciting endeavor, it is essential to prioritize the exploration of Earth first. By understanding our own planet, we can develop the knowledge, technologies, and inspiration necessary for responsible and successful exploration beyond Earth.

I recall a billionaire dying recently in their submarine project.

Of course, the rocket billionaires don't generally ride on the rockets themselves. So that's safer for them personally.

Submarines? whaddabout the children? whaddabout the climate? whaddabout Ukraine?

it's easier to make a case for exploiting space without any nation nagging at you about borders and sovereignty than it is for deep sea.

Money. Billions are not enough apparently.