Ok. I have to chime in here.
I am a PADI instructor and have taught the BSA Scuba program.
The Official BSA Scuba is not a certification. It is an experience. They can only get the BSA scuba patch. Which is not a merit badge. The idea is to get the boys exposed to scuba in a confined water only setting. They do have to pass as BSA swimming test and meet several other requirements (someone already posted these) to get the patch. This program is open to all boy scouts provided it is done with proper supervision. (i.e. conducted by PADI, NAUI, SSI instructor)
Confined water is defined by PADI (and other agencies) as a swimming pool or somewhere that offers pool-like conditions. This means that the confinement, water calarity, depth and entry/exit are similar to a swiming pool. There are places that meet this requirement. (i.e. springs in TX , NM and Florida, possibly tidal pools in the ocean.) But for the most part, think swimming pool. (Which works as a great activity for the winter months in a heated indoor pool, we did this program for 40 scouts in 4hrs one afternoon in Jan last year.)
Now where the 14yr age limit comes in. If you are doing scuba diving as a scouting activity. (including scuba training) i.e. have some already certified kids and want to do a combined BSA campout/diving trip. The kids have to be 14+, certified and be lead by an appropriate adult professional (i.e. Instructor, AI, DM)
Now as far as signing off somones BSA scuba patch, If they come and present me with a C-Card from SSI, PADI, NAUI. I already know they have met the diving requirements for the BSA Patch, because the C-Card requirements exceed the BSA requirements. I might have the boy demonstrate a couple of the skills in a pool or test his knowlege a bit. But personally, I would have no problem signing off the BSA patch.
This is kind of like a kid presenting his swiming merit badge and asking to get the 1st or 2nd class swiming requirement signed off.
For the most part I have kept the diving out of my son's scout troop, because the BSA is so restrictive with scuba as a scouting activity. (My son and I do lots of scuba+camping outings on our own and have a blast). However, we are looking at puting together a formal aquatics program for our Venture Crew. This will include swiming, snorkeling, scuba, sailing, boating, canoeing and kayaking, water ppolo, underwater hockey, etc.