Hi Duca,
This is not to discourage you, but to share my view of your situation so that you won't be disappointed.
I've never seen a Sandals, Club Med, Beaches, Iberostar or other large all-inclusive that could be considered a dedicated dive resort. I trust the latter is not what you are seeking. On the up side, there will be lots of activities, decent food, nice beach & a well-maintained property.
Your diving with Sandals will be with a highly mixed group, possibly including resort coursers & snorkelers, and tightly scheduled & regimented. On the up side, the boats are big & comfortable, and the op safety conscious.
Finally, Jamaica diving is considered very so-so by most experienced divers. Although the government has made real efforts in the past several years, long years of over-fishing & polluting of the reefs have taken their toll and will require a long time to heal. On the up side, the Dunn's River/Ochos Rios is quite scenic, with some cool sightseeing & river activities.
I suspect you'll enjoy yourself.
Best regards.
DocVikingo