http://www.navsea.navy.mil/Home/SUPSALV/ED-Divers/
The Navy Engineering Duty Officer (EDO, not to be confused with EOD community) is a restricted line officer community with some diving officer components.
It's a relatively small community, and I am not sure of the path from NROTC. All of the EDO officers I have known over the years got their Surface Warfare qualification first, then went to Naval Postgrad School for engineering master's, then on to their career as an EDO.
Special Warfare/SEAL officers have been known to dive now and then...