Nestled atop the breathtaking cliffs of Santorini lies a thriving tourist haven, yet beneath its idyllic facade, the ominous threat of volcanic peril simmers.

This enchanting Greek island was birthed from a colossal ancient eruption, which carved out a magnificent crater and created its iconic crescent shape. Now, researchers are delving into the potential dangers of the next explosive event.

Recently, BBC News embarked on an expedition aboard the British research vessel Discovery, seeking crucial insights into Santorini's subterranean activity.

Just weeks before their visit, nearly half of Santorini's 11,000 inhabitants fled to safety as a series of earthquakes rattled the island, starkly reminding locals of the tectonic instability hidden beneath the beautiful whitewashed houses, gourmet gyro restaurants, and verdant, volcanic vineyards.

Leading the investigation is Professor Isobel Yeo from the National Oceanography Centre, who emphasizes the underreported threat posed by underwater volcanoes, which make up about two-thirds of the world's volcanic activity.

"Many tend to overlook these submerged giants, assuming they are less dangerous than their more infamous counterparts like Vesuvius," she remarks, while engineers deploy an underwater robot to explore the depths below.

This research comes on the heels of recent seismic unrest in the area. The last major eruption in Santorini occurred in 1950, yet in 2012, significant geological activity indicated troubling signs of magma movement.

Yeo warns, "Underwater volcanoes have the potential for massive eruptions, and complacency can be dangerously misleading—each eruption can be drastically different from the last."

An example of such destruction is the 2022 Hunga Tunga eruption, the largest underwater explosion recorded, causing tsunamis and shockwaves felt as far away as the UK.

As Discovery navigates the waters above the volcanic areas, bubbling vents beneath hint at the dynamic geological forces at play. These hydrothermal vents, often found near volcanoes, spew hot water and gases, creating surreal underwater landscapes.

Yeo and her team aim to map these hydrothermal systems, gaining insights into how the mixing of seawater and magma influences volcanic behavior.

The expedition is centered on understanding the caldera of Santorini and the nearby Kolombo volcano, about 4.3 miles away, as they create comprehensive geological hazard maps for the Greek Civil Protection Agency.

Professor Paraskevi Nomikou, a geologist and local resident, underscores the importance of this research: "Our findings will help inform the community about the active volcanoes and the areas that will need to be evacuated in case of an eruption."

With the cost of such missions skyrocketing, Isobel insists on maximizing the team's efficiency with 12-hour shifts, as they gather volcanic samples that present both challenges and exciting scientific opportunities.

As the expedition unfolds, researchers are analyzing rock samples with intriguing properties, shedding light on the underwater volcanic environment.

To monitor seismic activity around the volcanoes, the team utilizes advanced technology, crafting a 3D map that connects the hydrothermal systems to the underlying magma chamber.

The urgency of their work was starkly illustrated during the recent earthquake scares, which revealed the island’s vulnerability and the heavy reliance of its economy on tourism.

Back on the island, locals are feeling the impact. Eva Rendl, a wedding photographer, reveals that business has slowed significantly due to cancellations following the quake swarm fears.

In a bustling square in Oia, British-Canadian tourist Janet echoes this sentiment, noting that several members of her group cancelled their trip. She believes that enhanced access to scientific information could help soothe fears and encourage tourism.

Nevertheless, the allure of Santorini remains irresistible. Newlyweds Tom and Kristina, undeterred by the underwater volcano risks, proudly announce their intent to honeymoon near a volcano.

Despite the lurking dangers, the paradise of Santorini continues to draw people in, revealing an intriguing juxtaposition of beauty and potential calamity.