1) The Navy has recently switched, diving is again a rate in the Navy for enlisted men. In the recent past diving was considered an additional duty rating although almost all Navy divers served in a diving position thier promotions and testing was conducted on whatever rate they were assigned (many were bosuns mate or engineman but they were at a disadvantage for testing because they did not normally work in the field) .The Navy has many different kinds of divers all with different missions, a decent book to check out is Navy Diver if your interested in that route.
2) The Army is currently undermanned in MOS 21D (diver) so positions for training are not all that hard to come by, on the downside there is still a fairly high attrition rate.
3) There are only a handful of dive oficer positions in the Army, if selected for one of these (8-10 positions for LT, only three positions for CPT) go into it knowing that after making captain (unless selected for one of the three command positions) you will have to leave the field, if you do get a command position you will have to leave the field after that tour.
4) Enlisted Army divers stay in the field for the duration of thier career (unless they elect to leave OCS, pilot, warrant officer, SF) and many at some point do take advantage of these other opportunities.
5) You can find more information on Army diving here:
http://groups.yahoo.com/group/armydiver/
I was an Army diver for 10.5 years and loved every minute of it. I was trained by the US Navy and have worked as an instructor in the Navy dive school, great bunch of guys to work with for the most part. I have also worked with Coast Guard, NOAA, Customs, US EPA, and Navy Sea-Bee divers and had great experiences with them all. Currently training is still held at the Navy dive school but it is a separate Army run course now.
In the Army you are going to be working in ports, inland waterways, and rivers. The diving is normally shallow 30-60 FSW and most often there is no visibility, the tasks are mostly construction or demolition oriented. You do get to do alot of diving in the Army and it does translate well to civilian work, especially inland diving (construction and demo)
I have some articles you can view on some missions the Army has done here:
http://www.rmediver.com/id26.html
If you have any questions or would like some POC's let me know,
jlane@rmediver.com