Staying under water forever

say i had 2 scuba tanks, 1 of them made hydrogen and oxygen using electrolysis on the salt water around it (assuming it's only salt water, no debris or anything alike). the other, a combustion engine and battery, the oxygen going to the diver and the hydrogen used to turn into energy, assuming i did not need food or water, could i stay under water with my contraption forever?

*with not "on"

no. Just no. Absolutely not. Even with perfect electrolysis, you will not last long.

also, you'd be better with dirty water, because that contains a bit of free oxygen and stuff you could potentially use a fuel. It works for fish

This is what nuclear submarines do to say underwater for months at a time.

i was looking more for an explanation for why it wouldn't work

OP doesn't know about fluorocarbon's

perfluorocarbon's*

aka liquid breathing

If you stayed above 33 feet, maybe, but for rebreathers that don't use nitrogen or helium. pure oxygen is poisonous below that depth.
Also, they have found that nitrogen does have a regulatory role in the body, so you need it.

>privides a concluding opinion

>uses a normative statement as a basis

You might as well be posting on /x/