There is no snorkling at all on Pattaya / Jomtien Beaches, unless of course you are interested in plastic bags, bottles, used condoms etc. Lonely planet are exactly right, you have to go out to one of the islands. The 'near islands', mainly koh Larn are the most popular for tourist trips and there are any amount of operators going to a beach on the island numerous times every day from Bali Hai Pier. Neighbouring Koh Sak is not frequented by the hordes of daytripers from Pattaya to the same extent, but is indeed easily accesible by booking a days snorkling on a diveboat, trampling all over the reef on a seawalker trip, or even taking an underwater tour in a Yellow Submarine which bounces along the seabed adjacent to the reef on the West side of the island, or privately hire a speedboat with driver (who will conveniently drop anchor for you right in the middle of the coral), and go on your own. Which ever option you select you will see the same, as most of the coral around these islands is at the shalowest of depths. Some of the better operators who actually care if their customers have a good day will go out to the 'far islands', where conditions are generally a little better.
You should have no trouble finding damaged reefs that you wish to photograph, as most operators and their thousands of customers seem to have little or no regard for the marine life, broken, damaged and dead coral is unfortunately most common in the Pattaya area.