The most reliable visibility in Costa Rica, short of going to Isla Del Coco, is at Isla Del Cano. We have been there only once when the vis was bad and that was the morning after an earthquake that was centered five miles south of the island. We have been to quite a few sites in the north and never seen as good vis as at Cano. There is always a lot to see. The only negative is the long boat trip if you are not staying at Drake Bay. From Uvita it is 42 miles each way. It has always been worth the boat ride, especially if you can arrange a three tank trip. We have been to Drake Bay and loved Corcovado Adventures Tent camp, but only did a snorkel trip because my wife was not yet a diver. Have made the trip from Ojochal and Uvita, Uvita is a little longer ride but Mad About Diving is a much better operation than Mystic Dive Center in Ojochal. This is my favorite part of Costa Rica, jungle covered mountains coming right down to the ocean, not so much development and a more laid back atmosphere. If you want to see the wildlife Costa Rica is known for, you will see a lot more of it in the south than in Guanacaste. Ojochal also has some really good restaurants and some cool places to stay.