We have been to Paradise Beach 3 times in the past 6 months.
It is a $12 -14 taxi ride for 4 (depending on where you dock or tender into) one way.
There is no entrance fee however, they do expect you to eat/drink there for the use of their free lounge chairs, tables, shade, clean restrooms, changing rooms, a clean "groomed" beach and showers.
There is an optional $9 wristband that you can purchase if you want to use their non motorized water toys. They have an iceberg, two trampolines, floats, snorkeling (deposit required that is returned when equipment is returned) and kayaks. They also have life vests for younger children who are not strong swimmers. Any snorkeling right off the beach is not going to be the best due to the iron rock in the water and the surf...however, it is a neat way to introduce folks who have never snorkeled before and don't want to pay a lot of money for the first time try.
The clarity of any of the water will depend on the weather systems that come through. I would recommend water shoes for any beach resort in Cozumel on the east side.
Paradise Beach's food and drink are safe and delicious. They offer free Internet at the bar.
There are all kinds of activities from independent vendors around. Parasailing (wrenched from the back of the boat ~which is safer than beach starts), jet skis, massages ($1 per minute with a 20 minute minimum), hair braiding. They have a coconut climbing tree attraction that looked interesting (although I have never tried it) and other beach activities.
Again the wristbands for $9 are optional. Both the boys get one when we go, but hubby and I do not.
If you are looking for a good beach day where you can do as little or as much as you want to...I would recommend this resort.