Some sauce:

"Nuclear subs, on the other hand, rely on the power generated by the nuclear reactor onboard. The reactor generates enough power to run all electronic and electrical systems onboard, in addition to the life support systems of the crew. Therefore, unlike diesel subs, nuclear subs can go for days, or even weeks on end without surfacing a single time. In fact, theoretically, a nuclear reactor onboard a submarine produces enough power to run the sub for a couple decades!"

https://www.scienceabc.com/innovation/why-do-submarines-have-to-resurface-can-they-remain-submerged-indefinitely.html

Nuclear subs also travel faster underwater:

https://navalpost.com/submarine-cavitation-drag-underwater-speed/