In my humble opinion, he Aquaman group has long suffred from lack of writer creativity. But in recent years we've seen interesting portrayals of them, whether in comics or an animated adaption. On thing that's bugs me is if you put them together, you'll see a lot of repeats with their powers.
Aquaman: With Orin you've got the best physical stats in the group, plus pretty respectable telepathy. However I've personally always been saddened by the annoying neglect of his trident. If Aquaman is to have any additional powers, they should come from his trident, which seems to be standard equipment for him at the moment. His trident should be firing blasts of magical energy, summoning storms, creating earthquakes, and manipulating very large volumes of water and even creating it. It's Poseidon's weapon after all. Or, should be.
Mera: She is actually one I've no gripe with. Though she tends to let her hydrokinesis do most of the work, it'd be nice to see her hitting tjings more.
Tempest: Garth's problem was solved in the 90s. He was given the ability to freeze oand boil water, as well as optic force beams. Now that's making him unique as an underwater hero.
Kaldur: The Young Justice cartoon got him just right IMO. He mixes hydrokinesis with hand to hand combat and weapons fighting, and sometimes gives an electric shock. Unlike Mera he gets up close to mix it up a lot.
Tula: Typical Atlantean abilities.
Lorena: Same as Tula.
So with that said, how would you diversify the Aquafamily so they all have something special to themselves?