Far below the rolling surface of the ocean lies a vast, little-known landscape of towering undersea mountains — and these submerged peaks are some of the most important habitats for sharks on Earth.

Known as seamounts, these giant structures are formed by ancient volcanoes that rise sharply from the ocean floor, sometimes reaching more than 1,000 metres high. Though invisible from above, they shape ocean currents, concentrate life, and act as powerful magnets for marine species — especially sharks.

Scientists estimate that more than 100,000 seamounts are scattered across the planet’s oceans, yet fewer than 0.1% have been explored. What researchers are now discovering is that these undersea mountains support extraordinary numbers of predators, far more than surrounding open waters.

Shark hotspots in the deep

Recent expeditions to Atlantic seamounts near Ascension Island revealed staggering concentrations of sharks. Researchers found that some shallow seamounts held up to 41 times more shark biomass than nearby ocean areas, along with far higher diversity of large predatory fish such as tuna.

Species including silky sharks, Galapagos sharks, yellowfin tuna and bigeye tuna appear to gather repeatedly at these sites. Some individuals leave nightly to hunt in open waters, travelling up to 100km, only to return before dawn.

“These places act like hubs,” says marine ecologist Sam Weber. “They’re not just feeding grounds — they’re meeting points, resting areas, and possibly navigation landmarks.”

Nature’s ocean engines

Seamounts don’t just attract life — they help create it. Ocean currents crashing into their steep slopes force cold, nutrient-rich water upward, fuelling plankton growth and feeding entire food webs. This process plays a role in around one-third of global ocean mixing, influencing how heat, oxygen and carbon move through the seas.

Some scientists believe sharks and whales may also use seamounts’ distinct magnetic signatures as navigational waypoints during long migrations, turning these underwater peaks into stepping stones across the oceans.

Oasis, hub — or service station?

Two main theories explain why predators gather at seamounts. The “oasis” hypothesis suggests that food is generated locally through nutrient upwelling. The “hub” hypothesis argues that animals feed elsewhere but return to seamounts to rest, socialise or mate.

A third idea — the “service station hypothesis” — suggests sharks use rising currents around seamounts to conserve energy. Because many shark species must swim constantly to breathe, these natural updrafts may give them a rare chance to rest while drifting in place.

A fragile stronghold under threat

Despite their importance, seamounts face severe pressure from industrial fishing. Bottom trawling — which drags heavy nets across the seafloor — can destroy centuries-old corals and sponges in minutes. Recovery may take decades, or may never happen at all.

Sharks are also heavily impacted by bycatch from longline fisheries, with hundreds of millions estimated to be killed each year worldwide.

Conservationists warn that protecting only the seamount peaks is not enough. Studies show their influence extends kilometres into surrounding waters, creating a “halo” of increased marine life that also needs protection.

Signs of change

Some countries are beginning to act. Portugal recently designated new marine protected areas around seamounts, and Ascension Island has closed its entire economic zone to commercial fishing. International bodies are now calling for a global end to bottom trawling on seamounts.

“Seamounts are irreplaceable,” says ocean governance expert Lydia Koehler. “They support predators that keep ocean ecosystems healthy — from the surface to the deep.”

Still mostly hidden and largely unexplored, these undersea mountains may hold the key to protecting sharks — and the balance of life in the world’s oceans.