Underwater Sci-fi?

Normally whenever someone does sci-fi, a common setting is outer space, and there's a good reason for that, we know almost nothing about space, thus we have greater freedom to make up our own stuff.

But something interesting I noticed is that of our entire ocean, which covers 70 percent of the entire planet, we've only explored 5 percent of it. Meaning there's a whole 95 percent of uncharted territory waiting to be explored.

Just think out loud here, what if there was a sci-fi adventure similar to a space epic, except the setting is underwater? I can picture sleek submarines, diving suits, cities encased in glass domes, bio-luminescent plant life and strange aquatic creatures that can be either friendly or hostile.

Now before you guys mention, I am aware that in a realistic scenario it would be more practical to just go out to space, not to mention the ocean might be polluted. The only way I counteract these problems is say that the future suggests Earth's population is exceeding the land mass (even though the planet itself is fine), and that we were so greedy with satellites that it was impossible to safely get any ship out of the atmosphere.

What do you guys think? Would you like to see sci-fi underwater epic?