Sandals usually includes diving in the price, however, if you manage to book the Sandals property in Jamaica that is partly timeshare (Sibonney was the old name I have no idea what name it goes by now), the AI fee you must pay via the timeshare actually excludes diving.
That is the one reason we chose to purchase Tradewinds Cruise Club. As an owner diving is included in the AI rate, and that includes all equipment required as well. There are a few locations that have an extra fee, because it is a national park, but that is the exception not the rule.