BSA has a Scuba Merit Badge, of which one of the six requirements is to earn an Open Water certification from a recognized agency. At one time that list was PADI, NAUI, SSI, IDEA, PDIC, SDI, and any member of WRSTC, although the list may have changed. An odd note is that one of the Merit Badge requirements is to earn the Swimming Merit Badge prior to starting on the Scuba Merit Badge. But of course nothing prevents a scout from getting certified without any mention of the merit badge. So I have to both wear and reconcile two hats when discussing the topic with a scout - PADI Instructor, and BSA Merit Badge counselor.
They also operate 3 National High Adventure Bases, one of which is the Florida Sea Base, which started out as a scuba program and grew into much more. PADI Open Water certification is one of the offered programs.
Sea Base Adventures
There are probably some regional High Adventure Camps or even just BSA Summer Camps that have also incorporated scuba into their program, but I am not personally aware of any. There are definitely guidelines available for those camps to operate a program. There may be added prerequisites for participation under the scouting umbrella, such as stricter age limits, but the actual scuba operation is left to the local contractor providing the program and the agency they teach.
There is also a "Scuba BSA" patch/program available, that is basically little more than a DSD experience. So if a local shop (assuming contracts, insurance, etc. is in order) is able to just swing by a camp once a week while in session and run a DSD in the pool, scouts can earn the cool patch and get a taste of scuba. A similar program is included in the National Jamborees, in a pool I think is no deeper than 3 or 4 feet.
If you want full details on other aquatic activity requirements, just Google "Guide to Safe Scouting." I think the requirement for using a canoe is to be a swimmer, or a beginner buddied with an adult skilled swimmer. For a rowboat, I think the buddy can be another scout that is a swimmer. Look over the Guide to Safe Scouting, they have done a pretty good job of covering every eventuality but it is definitely a living document with regular additions, revisions, and clarifications. Although I think those only happen once per year rather than quarterly, like a certain certification agency we all know.