In case anyone is interested - the University of Southampton are running their Shipwrecks and Submerged Worlds course again on futurelearn.com starting on the 25th May
I started it last time around, but became too busy to give it the time it deserved. What I did complete was very interesting. I'm signed up again for this time around though
Link for more information and to sign up is below - it's free to participate. I believe that if you want a certificate at the end then there is a cost for that - but having not got to the end I can't confirm.