I do not recommend getting certfied in PlayDelCarmen,because mainly there are no reefs there making your diving experience not all that it could be.I suggest taking the ferry over to Cozumel and doing it there.My husband and I just got back from a 2 week stay there,and I was already certified and my husband was not so we got him taken care of while we were there.We had a friend recommend using Eco Divers located downtown at the corner of 1st and 1oth,and we loved them.The instructor,Jorge,was very patient and knowledgable.We dove with them for 8 days and were very pleased with thier service.They even picked us up at the pier of our hotel.They were always on time and took us where we wanted to go,and they evn offered special rates for diving so many days in a row.I would definatley use them again the next time I go.Don't worry about using "valuable"vacation time getting certfied either,it only took my husband 3 days,and we dove the rest of the time.The water here is so clear and there is soooo much beauty here to see,I doubt that lake water would've been close to the same.I live in Austin,Tx and the only decent diving there is Lake Travis,which I won't dive now after seeing this water.It hardly compares.Good luck!I hope that your trip goes well.