Hi Leftwinger16, I was just at the El Senador in Dec 2005 and I dove with both Coco Dive (from the Tryp Hotel on the left side of El Senador) and with Blue Dive (from the Meila hotel on the right side of El Senador). The hotel itself is very nice, the layout is pretty good and the (live) entertainment seemed a lot better than the resort I stayed at in Playa del Carmen, Mexico. But I'll tell you why we ended up diving with both ops.
From various reviews on
www.debbiescaribbeanresortreviews.com we had the impression that Coco dive was the better op so we went with them. We booked 3 dives over two days. First, they refused to pick us up from El Senador so we had to trek across the beach with all of our gear, secondly this ops is kind of untrusting as they almost demanded payment upfront at the end of our first day even though we were going to be leaving thousands of dollars of dive gear behind to dry overnight and they made me go back to the hotel room, get the cash and come back all the while my gf/buddy stayed behind (as collateral??). As for the diving itself what really pissed me off is that they are unaccomodating. My gf was a bit slow getting into the water (backroll entry from their small boat as the big one was being repaired) so instead of waiting, the boat captain pushed her into the water!!! At the time I was already in the water on the opposite side of the boat so I didnt' know and couldn't say anything, I didn't find out later until we were back on shore. At the end of that same dive we came back to the beach and the same boat captain threw our gear into the water and let it float away while we were still gathering up our masks/fins/etc so I had to jump off the boat and chase down our BCDs before they floated away. Needless to say that was our last dive with Coco dive.
At that time I had read so-so reviews about Blue dive so we kind of decided that we wouldn't do anymore diving for the rest of our trip but as luck would have it our jungle excursion was cancelled so we mustered up and called Blue dive. Turns out this was a much better organized and run op in our opinion, the boats went out on time everyday and the DMs were much more friendly. They had new students and seasoned veterans and at no time did the DMs act cocky at all (unlike Coco dive). We were given in depth briefings, and most importantly they took us to much more interesting dive sites!!!
The prices for both are the same but we will never go back to Coco dive at the Tryp hotel, of course there are plenty of other good reviews for this op so YMMV. (and Blue dive will pick you up from the lobby of El Senador).