Over, under, sideways, and down are a few of the ways to explore, discover, and experience some of the planet's most spectacular landscape. Whether traversing over a sun-drenched desert to a refreshing oasis, going under the ground to ancient secretive caverns, zigzagging sideways down a snow-capped mountain, or walking down scenic backwoods trails, there's always something, somewhere to pique a traveler's interest.

One adventure that focuses on the "under" and "down" aspects is to strap on your scuba tank for an under-the-water excursion that takes you down to the mysterious depths of ocean floors around the world.

Underwater landscapes are one of Mother Nature's most interesting palettes with a plethora of diverse species, vegetation and formations, that create a spectacular stage of activity amid the sounds of silence.

Languishing amid the landscape are an array of sea creatures. Some are friendly, and some are not and observe you as closely as you observe them. Some reside among the dense vegetation, some choose the shifting sandy ocean floor, and others hide among the many crevices in rocks and coral reefs. Then there are those who make their special place to swim, play, and socialize in the eerie depths of watery graveyards where long-ago mariners, their ships, their cargo, and their crew came to rest.

Who knows what secrets these ships could tell about the intriguing history of their voyages as they traveled the waterways in the past, and are now gone to the peaceful quietness of their final resting place in oceans around the world. Discover history laced with the mystery of one of these underwater shipwrecks.

20 SS President Coolidge, Vanuatu

The SS President Coolidge is fascinating from stem to stern. Designed as a luxury liner in 1931, it served as a troop carrier from 1941-1942. The ship encountered mines while navigating Espiritu Santo resulting in its sinking. It resides in private waters and can only be accessed with a guide. While the ship remains virtually untouched in terms of relics, artifacts and cargo, the government prohibits any objects be removed, but the history, architecture, and exploration opportunities make up for it.

19 Kittiwake, Grand Cayman

The Kittiwake has an interesting history and if the hull could speak, it would most likely have some tales to tell. Back in the day, the vessel was responsible for transporting rescuees from submarines. Located near Seven Mile Beach, the vessel continues to serve in a rescue-type capacity as it is the platform for an artificial reef. Make the dive and enjoy the scenery but follow the rules in place for divers to Kittiwake.

18 Sea Tiger, Honolulu

The Sea Tiger met its fate while transporting illegal immigrants resulting in the Chinese trading ship being seized by the government. Instead of having the ship destroyed, it was decided to put it to good use as a haven for marine life. The shipwreck is touted as a top diving destination for viewing a variety of species from moray eels to sea turtles.

17 SS Yongala, Australia

The SS Yongala met its fate in 1911 when a cyclone tore through the area taking the wind figuratively out of the 360-foot ship's sails. Located approximately 95-feet down off the coast of Cape Bowling Green, it wasn't discovered until 1958. At the time of its sinking, a seven-day search resulted in no survivors. Divers are welcome to observe the ship from the outside. Inside entry is banned due to safety issues. The area surrounding the ship is brimming with a plethora of marine life.

16 SS Thistlegorm, Egypt

Exploration of the SS Thistlegorm is like finding a bonanza of prizes. The shipwreck resides in the Red Sea near Ras Muhammad National Park where it met its watery fate while taking a load of ammunition to Alexandria. When the German aircraft unloaded dual bombs, it sent the ship plunging into the sea. A visually stunning exterior and an equally surprising interior where the cargo of trucks and steam locomotives are still in the hold, make this dive a "must-see" on all levels.

15 USS Saratoga CV/3 Bikini Atoll

If you can add only a few dives to your itinerary, this is one that should be on the list. Sunk in 1946 due to a nuclear test blast, the massive 880-foot aircraft carrier is impressive on all levels. Exploration opportunities are intriguing as you wind your way in, out, and around the carrier's impressive features. The deck is located 90-feet down and the bridge is at 40-feet.

14 Nippo Maru, Chuuk

Truk Lagoon is one of the best diving destinations for history buffs as it was the main location for the Imperial Japanese Navy throughout the infamous war in the Pacific. The 348-foot freighter was one of the casualties. It is at a depth of 164-feet in an upright position with the deck about 130-feet down and the top about 98-feet down. Due to multiple naval vessels and transports destroyed, the area is rich in history, artifacts, and the ship's cargo.

13 Superior Producer, Curacao

Activity abounds at the 165-foot Superior Producer as you dive down 100-feet to explore the nooks and crannies of the freighter. This is a common destination for divers who like to swim among the fishes. You never know what might be lurking in the depths below, circling the boat, or observing you from the bow. From large barracudas to slim moray eels and colorful coral, the scene is ever-changing.

12 RMS Rhone, British Virgin Islands

The night time is the right time and that includes a diving adventure excursion to the Caribbean. In 1867, the RMS Rhone was built to last. Like the old Timex watch advertisement, the Rhone was designed to take a lickin' and keep on tickin' but a terrific storm made short shrift of the iron hull of the 310-foot ship and smashed it. Artifacts abound and once the sun sets, the murky depths become ablaze with orange coral.

11 Ray of Hope, Nassau, Bahamas

The retired 200-foot cargo ship was a donation from the Bahamian government for the sole purpose of it becoming an artificial reef. It rests serenely on the sand in a sloping position. The bow is about 40-feet and the stern at about 60-feet. Expect to see an assortment of marine life such as grey reef sharks roaming around, so we advise that you watch your back.

10 Hilma Hooker, Bonaire

The former drug-smuggling ship may not have gone up in smoke but it paid the price for its running when it was towed after experiencing technical difficulties. The 236-foot Dutch freighter raised suspicion when the crew couldn't produce proper paperwork at customs. Upon checking, it was determined the ship was being tracked by government agencies. This led to a search and the confiscation of 25,000 pounds of marijuana. Dive with caution.

9 SMS Kronpriz Wilhelm, Scapa Flow

Impressive by any means, the ship is massive at 146 meters in length. If you're interested in a leisurely scuba experience with plenty to explore, the Kronpriz is the one to set your sights on. It served as a battleship for the German Imperial Navy creating havoc wherever it sailed due to its size and its heavy-duty armaments. For those interested in military weapons, the ship's complement of guns is visible and accessible. The ship was scuttled in 1919 by the Germans. Take your time at this site as there is so much to see.

8 Carnatic, Red Sea

Launched in 1863 as a British clipper ship, the SS Carnatic met an unusual fate in 1869 when it ran aground on an island near the Gulf of Suez. The captain assured the passengers and crew that all was well and another ship was in-route to rescue them. During the night, rising waters shut down the boilers resulting in no lights or power. The following morning, the captain issued the abandon ship order but before passengers could disembark, the ship suddenly split in two resulting in the loss of many lives. The ship was carrying British gold. Some still believe there is a treasure to be found, and that is why the site remains a popular diving destination.

7 SS Andrea Doria, Nantucket

One of the most famous shipwrecks is that of the SS Andrea Doria. The ship collided in 1956 with the Stockholm out of Sweden resulting in the death of 46 passengers and crew members on the Andrea and 5 on the Stockholm. It is a sought-after diving destination but one that is considered dangerous and only for those with extensive experience. The ship lies 240-feet down and has extensive damage and deterioration but it still draws divers intrigued by the history, the mystery, and the possibility of finding an artifact or two.

6 Aida and Numidia, Red Sea

Two ships making their way through the tumultuous waters of the Red Sea came to rest near Big Brother Island. The Aida, which served as a transport for Egyptian troops, went to its watery grave in 1957 after unsuccessfully securing its mooring. The Numidia was an English freighter that met its fate in 1901. Both have sections that are intact providing an interesting dive. The Numidia is approximately 260-feet down and the Aida 100-to 200-feet beneath the surface.

5 USNS Gen. Hoyt S. Vandenberg, Key West

The 520-foot Vandenberg is an impressive site to see and due to the sheer size of the ship, provides diversity for divers. Weave in and out of the architecture and technology with an array of swimming buddies like the colorful moray eels. The ship resides in the waters of the Florida Keys National Marine Sanctuary at about 130-feet after being decommissioned by the U.S. Air Force.

4 U-352 German Submarine, North Carolina

Dive back in time to WWII when German U-Boats were trolling the waters along North Carolina's coast. In 1942, the German sub came up against the Icarus deployed by the U.S. Coast Guard and was subsequently sunk using a flurry of depth charges. The U-Boat is 218-feet long and served as home for 40 crew; 15 remain with the sub. At a depth of 115-feet, the sub offers an up-close look at several features of the war machine.

3 SS Cuba, Channel Islands National Marine Sanctuary

The SS Cuba has had several name changes. It was originally named the SS Coblenz and launched in 1897. The ship was seized by the U.S. in 1917 and renamed the SS Sachem. In 1920, a third name was attached when Pacific Mail purchased the ship and renamed it the SS Cuba. It served as transport for passengers and cargo to points in California and to Havana. In 1923, the ship plowed into a reef and ultimately sank. Today, the ship welcomes divers, archaeologists, and a plethora of fish species, dolphins, and seals.

2 Winfield Scott, Channel Islands National Marine Sanctuary

While exploring the SS Cuba, make your way to the Winfield Scott. The steamer ship sank in 1853. It is a beautiful underwater location with a continuously moving landscape as tall stalks of kelp surround the wreckage and gently move with the current, to and from. The Winfield Scott serves as an artificial reef so you'll see an abundance of fish species roaming around.

1 The Umbria, Sudan

The Umbria has an explosive history and that's putting it mildly. Originally launched in 1911 as the Bahia Blanca as a cargo ship, in 1918, the Argentinian government acquired the ship, and in 1935, it changed hands again and became the property of Italy. During that time, it was used to transport troops. In 1940, the ship was loaded with 360,000 bombs, detonators, weapons, and cars. Upon learning of Italy's entry into WWII, the captain ordered the crew to sink the ship, cargo and all, which is still with the wreckage. Dive with caution.