Colombia shallows, palencar gardens, paradise reef, the ship wrecks (off cafe del Mar), the reef off sunset Beach. Re: shore diving there is generally 3 ledges or sometimes two only or sometimes two and an uprising in the middle. 4-15ft. 25-45ft and 50-500ft (don't know the bottom of the wall.)
Another thought : If a diver was to stay 500ft away from the wall where the 'best' diving is there is still tons to enjoy and a downwelling would need to be remarkable to sweep that far as quickly enough to be dangerous. That would allow you to use a regular 2 tank boat dive instead of a custom charter or joining an OW class boat. Shore diving has its own challenges for a new diver and currents can be unpredictable in 30ft as well making the return to shore difficult. When the current is changing from North to SOUTH (as it often does this time of year) there is a period of rip tide that can be disorienting and difficult to swim against to get back to shore.
The 'house reefs' off blue angel, Casa del Mar, paradise divers, tikila restaurant, barracuda hotel etc all keep divers interested though the coral isn't 'Cozumel quality'. But a lot of fun can be had in 5-20ft with some curious critters and pretty things.
Regards,
Cameron