First off Edward, thank you for your service to our nation.
Thank you I did not serve long enough for my taste.
Ok so far. Divers who are totally paralyzed and can only move their heads get certified to SCUBA dive and have a great time. You don't have to be a great swimmer. You will want to ensure your instructor is Handicapped SCUBA Association (HSA) International certified. I say that because there are things about teaching individuals with a disability that are not readily apparent and if you have not been specifically trained to do it, you don't even know you don't know it.
I will check.
SCUBA is great for PTSD. It has helped many to archive a respite from the flashbacks, and to find a small space of peace. The being bone tired at the end of a day and the solid night sleep doesn't hurt either Many things, but most of all how to have a whole lot of fun and to do it safely. Part of the training focuses of the mechanics of diving, buoyancy control, not holding your breath ever, clearing ears, fining technique, clearing mask and regulator, and a whole bunch of it focuses on what to do if something happens (goes wrong) drills. These you will practice until they are simply natural reactions to the emergency stimulus. These include regulator recovery, regulator free flow and the ever popular "I am a dumb ass who doesn't check his/her air gauge and ran out of air drills.
The PTSD is probably not the culprit here. It is most likely your Traumatic Brain Injury (TBI) formerly called a concussion. How many times were you blown up? Each time takes its toll. Any time you work up after an incident you may have gotten a TBI. This means your short term memory is damaged. In about 2 weeks it moves to long term memory and you an access it. So you need to read it 3 times. The first time don't do anything but just read to get the overall picture. Reading 2 weeks ahead of the class will allow you to participate more fully in the class too.
I do not have TBI but PTSD and MDD (Major Depression Disorder) I do have short term memory issues and my future Dive instructor is aware of it.
My Doctor about hit the roof when I showed her the dive pirates website and others talking about how Scuba can help relax someone with PTSD all she kept saying was those people were irresponsible and putting people in danger that at any moment can have a panic attack and do something dangerous ie remove the O2.
A bunch. Oceanic has a grant of mask, fins, and snorkel available to you. Fins are the expensive part $80-300 with $180 being about right for a decent pair of fins.
The fins I liked (The look of) were almost $250 figuring on getting bright yellow everything to start so the Instructor can find me LOL
Enjoy and if I can help you find one of the many non-profits teaching near you let me know in a PM.