Suppose we're playing a supers game. I offer you a pregen character. The character has mid level super strength (not god like but good enough to bend steel, rip through a fortress wall with time etc.), limited invulnerability (bullets sting, a tank gun is still gonna kill you), the ability to travel at over one hundred miles per hour, and finally limited telepathy. Wait there's more. You have access to the technology of an ancient civilization and its resources in a pinch.
You need periodic immersion in water (in the old days every hour, nowadays a few hours or days depending on humidity.) Telepathy is mainly the control and communication with marine life. Travel is swimming. So you have fairly rapid travel over 71% of the Earth. The ancient civilization is Atlantis of course several centuries beyond our technology and with some elements of magic.
Water breathing supers are something of a joke in role playing games and comic books. Mostly due to 1) limitations on dry land, air, and space and 2) suffering by comparison. When Arizona is attacked by giant toxic space gerbils, face it, the water breather will get monitor duty. When your other team members can move small moons, run backwards in time or are the world's greatest sleuth commanding a bunch of sharks is no big deal. Especially in Arizona.
Suffering by comparison is a non-issue. Plenty of members in super teams fall way below the power levels of their big guns. You might have a demigod rubbing shoulders with a martial artist and a guy who can change colors or walk through walls (But not while changing colors … that's the catch.)
As for the limits out of water, why not create a team of water breathers? Everyone is a super hero of the undersea realms. Yes realms. Why have your water people be one type? Surface dwellers have diversified over thousands of years and they live on a piddling 12% or less of the Earth's surface (most of it near the oceans.) That's good enough for comic book style evolution!
Consider that a human with scuba gear can descend 40 meters and conventional submarines have a maximum depth of 500 meters. Most of the sea floor is at least a mile down and out of the reach of humans directly. More people have been to the Moon than the Marianas Trench. There's plenty of room to set up adventures in the unknown oceans.