Diesel submarines don't have to surface completely to recharge their batteries but they do have to come to snorkel depth. Some are now equipped with air independent propulsion (AIP) which enables them to stay submerged for longer periods. Interestingly, although the RAN acquired AIP for trials, it was not seen to offer sufficient benefit to fit it to the Collins class. The Collins class has demonstrated its capability in exercises with USN units in the Pacific.
An expert on the Collins class is gf0012-aust but I think he is on a business trip at present. Hopefully he might add information when he returns or correct errors in what I have said!