Here are the hurdles as I see them.

1. The process requires electrolysis to split the water. Combining an intake system without allowing electricity to escape into the water could be a problem.

2. A large copper coil is traditionally utilized for the electrolysis. Salt water would corrode the copper coil and the electronic connections.

3. The electronic output might disorient or attract sealife…including dangerous ones (sharks)

4. Oxygen is heavier than Hydrogen. It would be more difficult to extract the oxygen than the hydrogen.

5. The amount of air a diver needs changes as the depth of the water changes (compression). You’d need to ensure that the whole process would be protected much like an air tank.

Now, creating light, watertight, untraceable, made-as-required air devices would have great benefits to a number of markets. Commercially, recreationally, militarily, it would make a fantastic device. But it would have to be properly designed,easily fixed or replaced, and durable, and contaminate.

Still a worthy endeavor.