The main difference for snorkelers on the South side is that the reef structure is very near shore. A simple look at Google Earth will confirm this.
The additional consideration is the character of the reef structure. The coral heads start in very shallow water (1 - 15 fsw) and quickly break to a vertical wall structure that begins in similar depths. This particular zone is best evidenced in the area from French Harbor (Barefoot Key BFK) going Eastward to the area near Parrot Tree (PTR) on down to Media Luna (MLR) and Reef House Resort (RHR). I would also investigate access to these last two, (PTR is
not an easy snorkel), but remember there are two Media Lunas, this one is obviously on the South side. They do offer day access, and RHR might as well, but RHR is a bit of a hump necessitating a water taxi once you drive to Oak Ridge.
The Cruise Ship Pod People Trap is Little French Key (LFK) which has great snorkeling just to it's South. It might or might not be operational on non-ship days, and it might be cost prohibitive- but worth checking out. It is located just to the West of Fantasy Island.
Coco View does not do day dive visits. Fantasy Island (FIBR) does, but other than accessing it for this purpose, I really can not recommend it at this time. It will do nicely for a day trip. These two resorts share a channel which snorkelers actually spend full weeks at CCV during those high-end snorkel adventure naturalist tours (NatGeo and the like). The top of the walls are as clean as you can imagine, and on a calm day they present a superb shallow water opportunity, even for scuba. If you do this route, head over to the North side of the channel, cross over the wreck- it's too deep- and head for the
RED nav can to the East. Your adventure would start from there.
The access from BFK is a bit further inshore, and the snorkel depths, once you get clear of the result of French Harbor's long term effect itself, are a bit deep for all but advanced snorkelers. It can be a long shore SCUBA access for the vaunted "Mary's Place", the site mooring for which is quite a ways offshore and sits in 40' on a flat coral plateau.
Many, many people have peeked u/w from making entry on West End zones. Very few,
comparatively, have dived the South side. A microscopic number have done both, but everyone will have their favorite and best, no matter what.
See it all. For being such a small island, the underwater architecture is widely varied and very poorly understood.