The best snorkeling in Bermuda will be out over 'n around the offshore barrier reef system. To get out the these areas you'll need to sign on with one of the local snorkeling excursion/tour operators.
FANTASEA--
http://www.fantasea.bm/snorkeling/
JESSE JAMES--
http://www.jessiejames.bm/
SNORKEL BERMUDA--
http://www.snorkelbermuda.com/
OR...to reach some of the near barrier reef areas off of Bermuda's western shore, rent a small (13'-17') outboard powered (30-35 hp) self-drive skiff--
H2O SPORTS BERMUDA--
http://www.h2osportsbermuda.com/
SOMERSET BRIDGE WATERSPORTS--
http://www.bdawatersports.com/
For the best snorkeling-from-the-beach, you can take a 'regular' #7--Dockyard-Via South Shore Beaches-Hamilton (NOT a '..Special') from the landward end of your king's/Heritage Wharf cruise ship pier, approx. 28-30 mins. to CHURCH BAY.
As an alternative, you could take an ORANGE--Dockyard-Saint George's route public ferry, from the ferry dock at the end of the pier to SAINT GEORGE'S...then either walk or take a taxi the 1/2 mile to TOBACCO BAY.
There are concessionaires at both CHURCH BAY and TOBACCO BAY that rent basic snorkeling gear.
Edited: 2:11 am, February 11, 2013