Hi Damika and welcome!
You can snorkel from the resort beach. Have the bellboys drive you and leave you off at the Kantenah beach. Right in front of the Mayan suites there you can snorkel. There is a reef a little deeper out. You can also walk to the salt water pool (south) and snorkel there. You can take a snorkel trip through the on-site dive shop or take a taxi to Akumal Bay and snorkel there (no tour needed)
You can easily get to Tulum on your own via colectivo (public van) or taxi and hire a guide there. If you want to do Coba, Chichen Itza, Ek Balaam or other ruins you can hire a private guide like Monica
Monica Tours
or hire a private company such as Agi Tours to customize something for you.
Agi Tours
I hope this helps.