We went there during Christmas 3 weeks back. This was my first dive and had a great experience. They really make you comfortable first and the briefing is very good. I enjoyed my first 6 meter dive and the same afternoon did 12 meters again. Cannot find any fault - good people, good equipment - know their stuff well ! They took underwater photos as well (which was good). 

Given my experience - my wife (who is a non swimmer) also gave it a go and she also enjoyed the experience.

If you are a first timer like me - I would not hesitate to recommend them.

Aditya S, http://www.tripadvisor.com/ShowUserReviews-g662290-d1382723-r248672354-Manta_Diving_Lanzarote-Puerto_Del_Carmen_Lanzarote_Canary_Islands.html#REVIEWS