Former Royal Marine Mr Aldo Kane has led expeditions in extreme environments all around the globe, from the mangrove swamps of Borneo to remote rivers in New Guinea and tracking tiger hunters in southeast Asia. Oh, and he was part of a team that broke the world record for rowing across the Atlantic. Normally to be found supporting scientists and filmmakers in extreme environments, he’s most famous for leading an expedition into the erupting crater of Mount Nyirangongo, one of the world’s most active volcanoes, in the Democratic Republic of Congo. “What I’m particularly good at is operating in extreme environments where the work is hard, wet and horrible,” he says. “It’s life fast forwarded to a million miles an hour and usually in support of someone doing something very cool.”

What motivates you to put yourself in perilous situations?

It’s an attraction to the unknown, to testing myself physically and mentally and finding out where my limits are. I was a sniper in the Marines and had that ‘live by the sword, die by the sword’ mentality, in which your decisions are what allow you to succeed or fail, and it’s completely your responsibility. Now I can apply that in extreme remote or hostile environments.

What’s the toughest scrape you’ve been in?

I’ve gone inside volcanoes three or four times. It’s one of the most extreme environments on planet Earth. Absolutely everything is out to get you – poisonous gas, extreme heat, lava bombs, CO2 sinks, rock falls, huge hailstones – but it’s also a monumental logistics challenge and hard physical labour getting equipment in there. It might take someone pretty capable four hours to do a round trip from the top of the volcano to the campsite. I probably did 12 runs in 24 hours.

What does toughness mean to you?

To me, it means getting on with the job in hand without complaining and moaning about it. Some of the hardest men I ever met in the Royal Marines could be small and softly spoken, but they can take anything. You can be the toughest person in lots of different circumstances, but you’re always one step from away from having your arse handed to you. The minute your ego gets on top of you, you’ll be slain. But if you have the physical and emotional resilience to crack on when it’s cold, wet, difficult and grim, then you really are tough.

Mr Aldo Kane’s watch: the Bremont MBIII

It’s thanks to Martin-Baker, the British supplier of ejector seats to the world’s air forces, that Bremont is able to say that its MB watches are “tested beyond endurance”. They are subjected to the same tests as Martin-Baker’s ejector seats. That includes the extreme G-forces of a live ejection, vibration simulation, extreme temperature endurance and salt fog and humidity testing to recreate aircraft carrier deck conditions. With a hardened steel case, rubberised anti-shock movement mounting and rotating inner bezel, it’s small wonder that the MBII (automatic) and MBIII (additional GMT functionality) have provided the base model for many of Bremont’s military collaborations. “I need something that’s bombproof,” says former military man Kane. “When you’re in a volcano, everything metal corrodes in no time. Sulphur dioxide in the atmosphere gets wet, creates sulphuric acid and destroys your kit. I had my MBIII on for three weeks and it’s one of the only bits of kit that didn’t get trashed by the elements.”

For her day job, Ms Anna von Boetticher trains military divers from the German navy in breath-holding and underwater techniques that she has perfected as a competitive free diver. Her real passion is for exploring the depths on a single breath in locations around the world, including a series of extraordinary dives amid the icebergs of Greenland. “Physically, I’m the anti-free diver,” she says. “I have a lung capacity that’s 25 per cent too small for my body size and I get a very early desire to breathe that comes on very fast. I’m also not a super good swimmer technically, so it’s a hard training battle. I’m not built for it, but mentally I really am and that makes more of a difference in the end.”

What motivates you to put yourself in perilous situations?

It’s firstly a desire to explore, to put yourself out there. I always get asked, ‘What did you see down there? How deep did you go?’ It doesn’t matter. I don’t go to see a fish or a reef necessarily. It’s more for the physical experience of being there, in that place you’re not supposed to go and to feel this world around you where you’re not meant to be. There’s always a moment where I open my eyes and take in this space, the light and magic of the deep. It’s always different and very special.

What’s the toughest scrape you’ve been in?

I’ve done a lot of free diving beneath the ice. I’m drawn to the wild places and the Arctic and Antarctic are among the wildest we have. It’s a kind of minimalism that forces you to engage with your surroundings on that basic level. In theory, cold water is helpful to a free diver because the dive response is stronger as your body recognises that it’s in water, not in air. When you start to shiver and get really cold, however, you need a lot of energy to keep you warm, which uses oxygen that’s not available to hold your breath.

More recently, I used this experience in a completely new way, by diving into a crevasse in the Alps, near Chamonix. I had to learn ice climbing. It took a year to train and practise and to explore locations. I was wearing crampons with a wetsuit. We fixed up anchor points with ice screws and I got lowered in. I didn’t think it would be so deep, but I just let myself sink and I didn’t even find the bottom. The walls of ice were so narrow and sheer, so you can’t push yourself at all. I could only move with the crampons and an ice axe. It was dark. It was very mysterious. I could feel the walls close in. You really did feel inside the glacier.

What does toughness mean to you?

It means taking responsibility. You have to be hyper aware of the risks and you have to know about yourself before you go there and know that you’re not going to panic in a tricky situation. I’ve got lost beneath the ice before. I surfaced and realised the hole in the ice wasn’t where I expected it to be. I remember thinking this is a new level of problem, but then you have to work out how to solve it, which means going back down and looking up again, still on the same breath. It takes years of experience of all kinds of diving situations to be able to do this.

Ms Anna von Boetticher’s watch: the Oris Aquis Depth Gauge

Rated to a depth of 500m, the Oris Aquis Depth Gauge is one of the simplest, and yet most ingenious, takes on the idea of a dive watch that offers a mechanical depth read-out. Effectively Boyle’s law in watch form, it features a hole in the dial through which water flows into a channel in the sapphire crystal. As the air in the channel is compressed at depth, more water flows in, which creates a watermark corresponding to a yellow gauge indication running around the dial. “It speaks to my heart as a diver,” says von Boetticher. “The pure simplicity of the physics, just air being compressed in a channel at the same rate as the air in my lungs. The effect of physics on my body is the same as in the watch and that’s such an amazing solution.”

If there’s any form of physical endurance activity Mr Andy Torbet cannot do, he seems yet to have found it. The former paratrooper, anti-terrorist operative and underwater bomb disposal expert can be found on any given day skydiving (he’s a member of the British team), scaling mountains, deep-sea diving or exploring unmapped underwater cave systems, the latter being a particular obsession of late. “It can be incredibly oppressive,” he says. “You’re in the dark, underwater, dragging your kit behind you and surfacing in chambers many kilometres from where you started, but you’re going to places no one has seen before.”

What motivates you to put yourself in perilous situations?

I like the idea of overcoming challenges and of getting to places it shouldn’t be possible to get to. It brings a sense of focus and purpose and a reason to train. True exploration now requires the highest degree of technical skill and risk management to reach new places and make discoveries. People assume you’re a thrill seeker, but I’m actually very risk averse. You either hope that something isn’t going to happen or you assume that it is and you’re prepared to deal with it.

What’s the toughest scrape you’ve been in?

Early in my cave-diving career I was in Scotland’s deepest cave. It’s called the Cave of Skulls for a reason. At the bottom there’s something called the Letterbox, a slot in the cave wall that leads to an underwater sump, which no one had been through since a solo diver did it in the 1970s. It’s 15ft long and I had to dig out the silt in it to fit through it on my front, dragging my kit behind me. I was breathing through the side of my mouth with my face pressed against the ceiling in the gap above the water, but the last few feet are underwater. I plunged in, gave a big push and got completely stuck. I remember how painfully cold the water was in my eardrums. You have to fight the urge to panic and work out what to do. I realised the mistake I’d made was to take a deep breath. It feels counter-intuitive, but I exhaled as much as I could to reduce the size of my chest, which gave me just enough space to push through.

What does toughness mean to you?

Most things are mental, even the physical stuff. I built a gym in an outhouse at my home and, most of the time, I’m either training there or diving, skydiving or climbing. I train because I enjoy being capable, because my projects demand it and because fitness is an essential tool, but you start with the mindset. In cave diving you’re alone, underwater, underground and in the dark. You have to build a resilient mind that can appreciate the bigger picture, but also focus in on the problem in front of you without spinning out of control.

Mr Andy Torbet’s watch: the Panerai Submersible Marina Militare Carbotech

The Marina Militare is the modern descendant of the hulking watches Panerai made for Italy’s underwater commandos in the 1940s and comes with all the robust dive credentials you’d expect: 300m water resistance, high legibility, a redoubtable automatic movement and the crown-protection system that’s a Panerai calling card. It is Panerai’s proprietary Carbotech material that elevates it from the merely hardy to the seriously hardcore. The case, dial and bezel are all made from this special carbon composite, which is both lightweight and seriously resilient. Carbotech’s uniquely textured grain gives the watch its stealthy, dark camo-like appearance – not that the aesthetic is front of mind for Torbet. “I operate in conditions that are unforgiving to sub-optimal equipment and I care less about what it looks like and more about the fact that as a survival tool in extreme environments, it’ll keep me alive.” Indeed “Survival Instrument” is exactly what is engraved on the back.