I have not had the opportunity yet, but if you dive with ATI Divers and get your logbook stamped, you will be entitled to discounted diving throughout Central America.
If you have Facebook, enter TrekCats and you will find a group of 7 dive operators throughout CA (Costa Rica, Utila, Nicaragua, Panama, Colombia-I know it is S. America, but they are participating as well). TrekCats offers discounts to divers who are trekking through the region and utilize recommended dive operations.
The group is in its infancy and its web site is under construction, but its Facebook group has been operational since April and we've had many divers take advantage of the discounts. All that is required is to have log books stamped by one of the participating operators since April 1, 2009.