You do not need to be exeptionally fit to dive. However, diving does mean exposing yourself to an normally alien environment which can have an effect on your body. We need to make sure we are all safe underwater .
BSAC is advised by the UK Diving Medical Committee (UKDMC) who supply a list of approved diving medical referees.
The first step for you would be to fill out the recreational diving medical declaration which you can download here.
If you can answer "NO" to all questions, you are good to go!
Should you need to answer "YES" to any question, you are advised to seek consultation with a medical referee. UKDMC approved medical referees have an aditional qualification for scuba diving related medical matters which a normal GP typically does not have.