(CNN) — Tired of the Caribbean? Called at every Mediterranean port? Bored of the Alaskan fjords and the Baltic capitals?

An entirely new body of water may soon be open to intrepid cruise fans seeking new horizons.

The only issue: It's a landlocked sea surrounded by some of the world's most cloistered countries. But for many travel adventurers, this will be part of the appeal.

Besides its fame as the main source of prized black caviar, the Caspian Sea is the world's largest inland body of water.

In fact, for a long time, not even the five countries that share it -- Azerbaijan , Russia, Kazakhstan, Turkmenistan and Iran -- could agree on whether it is a lake or a sea.

But with the decades-long dispute over its legal status resolved, the sea is now open to luxury cruising.

Sea or lake?

The question of whether the Caspian is a lake or sea is about more than just semantics.

Before the collapse of the Soviet Union in 1991, only two countries bordered the Caspian Sea: Iran and the USSR.

For the 27 years that followed, the five countries that now had a claim to these resource-rich waters were locked in a dispute over its status.

There's plenty at stake: It's home to caviar-producing sturgeon (although fishing is currently subject to a conservation-led ban) and there are estimated reserves of around 50 billion barrels of oil and 290 trillion cubic feet of natural gas.

If the Caspian's a sea, then international law states that the seabed would be divided according to each country's coastline. That would benefit Kazakstan, with the longest shoreline, but disenfranchise Iran, which has the shortest.

If it's a lake, however, then the seabed would be divided equally.

In August 2018, leaders from the five nations met in the Kazakh coastal city of Aktau to sign a landmark deal which grants each country 15 miles of sovereign waters, a further 10 nautical miles of fishing area, and then common waters beyond.

The Caspian now has special legal status, so that it has still not been declared lake or sea. The question of how to divide subsoil territory has been put off for now, but what it does mean is that the waters are now open for new tourism opportunities, including cruising.

A versatile ship

l e v a r t

A brand new cruise ship, the Peter the Great, is currently under construction in Astrakhan, a Russian port city at the mouth of the river Volga.

The ship will have 155 cabins and capacity for 310 passengers and is expected to launch this summer, although specific dates have not been announced and itineraries are not yet on sale.

Its operator, the Moscow River Shipping Company is said to be planning one- and two-week itineraries around the Caspian Sea, calling at ports in Azerbaijan, Russia, Kazakhstan, Turkmenistan and Iran.

The dimensions and design of this 141-meter by 16.8-meter ship will also make it possible for it to move through Russia's network of internal waterways. This means that it'll not be confined to the Caspian and will eventually be able to reach the Baltic and Black Seas.

Although no sailing program has been made official, reports in the Azerbaijani and Russian media indicate that the ship will alternate the Caspian cruises in winter with river itineraries along the Volga and between Moscow and Saint Petersburg in the summer. It may also conduct cruises in the Black Sea, along the Russian coast and all the way to Georgia and to the Turkish city of Trabzon.

It's likely that it will be the first of several new cruise offerings, though there is still work to be done on tourism infrastructure in the region as a whole.

Russian rivers

River cruises are quite a long-established business in Russia, with a number of local operators plying the country's main rivers.

Russian rivers have even spawned a global cruise brand. Viking Cruises, now a major player name in the luxury cruise industry, traces its roots back to a small four-boat riverine operation started by a Norwegian entrepreneur in Russia in the 1990s.

Viking continues to have a strong operation in the country, with some 12,000 visitors carried through Russian waterways in 2018.

Moving into the Caspian may open up a new area of growth for the Russian cruise industry.

Although not as common as those in the open seas, cruises through landlocked "seas" (or lakes, to be more accurate) have already some tradition in more mature markets, such as North America.

"We're seeing more and more interest in the Great Lakes and their associated ports from people who visit our site. It's a great fit for people looking for something a little different," says Colleen McDaniel, senior executive editor of Cruise Critic.

"Ships that sail these itineraries tend to be a bit smaller, and focus on board is heavily skewed toward enrichment, as a big draw for these itineraries is history. Ships are comfortable and feature great dining, often with local flavors, but don't expect waterslides or rock-climbing walls. The ports are the stars."

What's in store for passengers?

The city of Derbent and the Caspian Sea beyond, as seen from the walls of Derbent Fortress. Shutterstock

At more than 370,000 sq kilometers (143,000 sq miles), the Caspian is considerably larger than all of North America's Great Lakes combined, to which you can add the diversity of natural ecosystems and civilizations that have thrived along its shores. Passengers on the Peter the Great will have no shortage of sights and attractions to visit.

They will be able to enjoy the charms of the Azerbaijani capital, Baku , the largest city on the Caspian shore and its likely base port, but also ancient cities such as Derbent, at the southern tip of Russia, the deserts on the sea's eastern shore and Iran's subtropical riviera.

But before you get too excited, you'd better check each of these countries' visa requirements.

In the case of Iran, for example, the US State Department has a travel advisory note advising American citizens not to visit the country at all.

Even if you're not a US citizen, a recent visit to Iran may complicate later trips to the United States. For example, you would be denied access to the ESTA program, and you would then need to apply for a visa at your nearest US Embassy, plus you may be subject to additional scrutiny at the border ( as former NATO secretary general Javier Solana found last year ).

Azerbaijan has simplified its visa restrictions in recent years, introducing a quick-access electronic visa for which close to 100 countries are eligible.

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Game-changer

In any case, the majority passengers on this new cruise is likely to be Russian citizens, followed by those of the other Caspian countries.

"We are confident in the prospects of these cruises and we are looking forward to the entry of the ship Peter the Great. We expect great demand and interest in this product," says Denis Kreitsberg, managing director of Kruiz.online, a Russian cruise marketplace.

These developments also fit with the current growth of the Russian cruise market.

"We are seeing growth rates of 15-20% annually in the number of Russians that go on sea cruises. Most of these travel abroad to complete a cruise," says Fedor Egorov, managing director of Dreamlines Russia, the local branch of the international cruise portal of the same name.

Perhaps fittingly, this new ship is named after the czar who, in the early 18th century, campaigned extensively in the Caspian region, conquering large swathes of land along the way.