1. Cozumel, Mexico

Arrive by ship to the town of San Miguel and then head straight to Scuba Club Cozumel, 1 mile south of the downtown ferry dock. There, you can shore-dive the house reef or, if you arrive by 2:30 p.m., join a one-tank boat tour.

Choose the latter, and odds are good — 3-in-7 — that you’ll visit the C-53 wreck (in its former life, the Mexican navy vessel Felipe Xicotencatl).

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Purpose-sunk in 1999 to 82 feet, it offers safe penetration of the interior corridors, galley, and engine and radio rooms. Those who wish to remain on the perimeter will likely be graced with barracuda and grouper visits, and even eagle ray flybys. scubaclubcozumel.com

2. Roatan, Honduras

The first boat of the day at Tranquilseas Eco Lodge on Roatan leaves at 8:30 a.m. It’s likely headed to the wreck of the M/V Aguila, or a wall dive in the Sandy Bay area.

The structure of the 230-foot former cargo ship — in pieces at 100 feet — is intriguing for its nooks that shelter crabs and spotted moray eels, but it’s the dog snapper and tiger grouper dive-bombing the shallower stretches of the wreck that prove most compelling.

If your group heads to the wall, you’ll have to work a bit harder to locate the choice find. Toadfish camp out in dens there, visible only for the tiny portions that jut out.

Says Junior Mora, manager of the resort’s dive shop, “You have to really comb the reef. They have only a bit of smile and beard showing, but they are always there.” tranquilseas.com

3. Grand Cayman

It’s exactly 1 mile — five minutes by taxi — from where cruise-ship tenders land in George Town to Sunset House. There, the simplest option is shore-diving the house reef.

“We charge $12 a tank, so compared with what you’d pay on the cruise, you could get three dives in with a buddy during your stay and have lunch together for less than it costs for one excursion,” says Keith Sahm, manager of Sunset House.

Drop in, and you’ll meet Amphitrite, the mermaid-looking statue in the resort’s underwater front lawn. She’s seen a dozen marriage proposals, as well as innumerable selfies.

Keep heading offshore to encounter smaller finds, like lettuce sea slugs and other nudibranchs, plus a litany of crabs. sunsethouse.com

4. Key West, Florida

Step off your cruise ship in Key West, and if you can make Southpoint Divers’ departure time at 8 a.m. for the morning boat or 1 p.m. for the afternoon tour, then you’ll likely set fin atop the USNS General Hoyt S. Vandenberg. By the numbers, the average cruise ship is 1,187 feet, and the Vandy is nearly half that — stretching 524 feet.

It’s the size that most stands out in people’s minds, so impressive that it warrants a second dive, all possible before it’s time to return to the cruise-ship pier. southpointdivers.com

5. Grand Turk, Turks and Caicos

“We don’t make any changes just because someone is visiting by cruise ship,” says Vicky Dunsten, activities coordinator for Blue Water Divers. The one difference is arrangements must be made ahead of time to en- sure time isn’t wasted in the store with gear and paperwork.

From the Grand Turk Cruise Center, Blue Water Divers is less than a mile away; dive-boat departure times depend on a vessel’s arrival time.

You’ll most likely dive the wall in Columbus Landfall National Marine Park, and if Dunsten has a say, it’ll be McDonald’s, popular for the archway in the reef.

Says Dunsten, “There’s a wonderful contrast of color against a backdrop of very white sand.” facebook.com/bluewaterdiversgrandturk

6. Kauai, Hawaii

The most popular dive site on Kauai is Sheraton Caverns — and, yes, it’s doable during a cruise-ship drop-in.

You’ll miss the morning dive, but the afternoon trip is an option if you arrive by 12:30 p.m. to Seasport Divers, 20 minutes by cab from Nawiliwili Harbor.

The only difference between the morning and afternoon dives is that you’ll follow a shallower profile later in the day — no big sacrifice given the site’s profile is between 25 and 65 feet.

As for wildlife, says Marvin Otsuji, owner of Seasport Divers, “You name it, we see it there.”

The list of the caverns’ locals includes zebra, yellow margin and dragon moray eels, plus passing manta rays.

Inside each room, says Otsuji, “there could be a sleeping turtle or whitetip shark, but it’s the topography that makes this a really easy and memorable dive.” seasportdivers.com

7. St. Thomas, U.S. Virgin Islands

“Armando’s Paradise has the greatest amount of sea life,” says Doug Sprotte of the site that St. Thomas Diving Club regularly shows cruise-ship passengers. It’s five minutes by boat from the scuba center’s dock — itself a 10-minute cab ride from the Havensight pier. If divers arrive to the shop by 8:15 a.m., they can be back aboard their vessel no later than 11:30 a.m.

The site itself is a pinnacle between 15 and 40 feet deep, giving ample bottom time to spot octopuses and mingle with lobsters, eels and schooling creole wrasse. stthomasdivingclub.com

8. St. Maarten

The biggest hurdle to diving St. Maarten when arriving via cruise ship is coordinating the times. Often ship time is one hour behind island time, making it easy to miss the dive boat.

Plan ahead, and you will make the 8:40 a.m. arrival time at St. Maarten Dive Adventures shop in Divi Little Bay.

From there, you’ll likely dive the HMS Proselyte. The frigate ship lies in 45 feet of water, allowing time to peruse the cannons, ballast bars and anchors. stmaartendive.com

9. Tortola, British Virgin Islands

“You control the itinerary,” says Mike Rowe, course director for Sail Caribbean Divers, of booking a private excursion through his Tortola-based outfit. Whether you’re making the reservation for one, two or 24 guests — the fleet of four dive boats, including a 46-foot vessel, caters to groups of all sizes — you’ll walk off the cruise ship’s gang plank and immediately onto the dive vessel to start a half- or full-day getaway.

Where you’ll head is entirely your choice. Sail Caribbean Divers also sends a guide with each private charter, so you get more one-on-one contact with the critters he points out, or get help brushing up on skills if you’re rusty.

“Scheduled cruise-ship excursions are held to very strict timelines,” says Rowe. “But with private excursions, there’s so much flexibility.” sailcaribbeandivers.com

10. Nassau, Bahamas

If you want to hang with the big boys of Nassau — Caribbean reef sharks, that is — you have to know when your ship leaves the port of Prince George Wharf. If it’s 6 p.m. or later, then you can join Stuart Cove’s Dive Bahamas for the afternoon feed, where you’ll kneel in the sand as these scavengers — along with a resident black grouper — snap up herring just inches from your face.

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If your cruise ship is departing sooner, you have the option of making a morning dive.

Either way, Stuart Cove’s van will collect you from the cruise- ship terminal; morning pickups happen at 7:45 a.m., and the afternoon pickup time is at 11:45 a.m. stuartcove.com