If your ship docks in Havensight(most likely) Saphire is about 10 to 12 minutes by cab. If you dock sub base, the plan on half hour. Fare from Havensight about $6 to $7 per person, about a dollar or two more from sub base. The mileage isn't all that different, you fight downtown traffic in the morning from Sub base. You might negotiate a "rate" with a driver if there are four of you. Agree on a price before you take off.
Get off the ship first thing and head out to the beach. Swim, snorkel,
other beach/water toys available from activity desk. Food options include a restaurant , bar (sells food) and convenience store that also sells food and snacks and cold drinks. There are toilets and an outdoor shower.
Cab stand is out in front of the resort lobby.
Stay 4 hours or so on the beach go to tram, have lunch and then shop Havensight for convenience or go into town. Leave a minimum of an hour to get to port from town because EVERYONE is headed back at once)(this is why I suggest you shop Havensight).