For diving, there has been some experimental use of hydrogen as a partial replacement for helium in breathing gas mixtures. This obviously increases the risk of fires and the physiological effects aren't fully understood. But it might eventually be used in commercial, military, and exploration diving for those cases where we need to send humans really deep and using an atmospheric suit isn't an option. Regular sport divers will probably never breathe hydrogen.
For divers, we really should be focusing on building better underwater drones. Remove the risk to human life entirely. You don't need AI either, just a remote-controlled machine with a cable that goes up to the surface. I know there is some loss in dexterity with current robot arms, but building more dexterous system seems like it's not an impossible task.
ROVs have already reduced the demand for commercial divers on some types of work. But it's going to take decades (if ever) until they're able to do the full range of human tasks. Some construction work has to be done essentially by feel in near-zero visibility so using an ROV for that would require advanced force feedback mechanisms, maybe imaging sonar and other sensors. Not necessarily impossible, but extraordinarily difficult and extremely expensive with current technology.
For sport and exploration divers, going there yourself is kind of the whole point. I'm not interested in watching a video feed from an underwater drone.