Diving the deepest trench in the world with Tim Macdonald

24th June 2021 Jack O'Rourke

Diving the deepest trench in the world with Tim Macdonald

This year, Australian sub pilot Tim Macdonald became the deepest-diving Australian with a 10,925-metre journey to the Challenger Deep at the bottom of the Mariana Trench. Alongside his co-pilot New Zealander Rob McCallum, the duo completed “the ANZAC dive” over 12 hours in Limiting Factor, the world’s first reusable full ocean depth submersible.

For Tim, this record is a culmination of years chasing a life-long goal of becoming a sub pilot that has taken him around the world to the deepest oceans. 

Tim has been in and around the water from an early age.

“When we lived in Western New South Wales we used to tow the trailer boat up to the Whitsundays and we would camp out on the island for a week at a time,” says Tim Macdonald. “I was six or seven at the time and it was a lot of fun. We would camp on shore, and get around the islands by boat, fishing, camping, diving and exploring.”

Chasing a passion

His relationship with the ocean changed when the family moved to Nelson Bay, and Tim would spend all day boating and diving with his dad, then work at the local dive shop filling tanks and washing gear. That period fuelled his passion for diving, and the world under water.

“I started as a dive instructor and boat skipper, and then moved to Tasmania to study marine and offshore engineering at the Australian Maritime College. Usually, it's a four-year degree, but I took a part-time approach,” jokes Tim.

“I did three years, and in my summer holidays I was going overseas as a dive instructor. I ended up working on some private yachts and was offered a job on an expedition research superyacht. I worked for those guys for about 4 years. I studied off and on all while working on different research vessels.”

Tim worked on those research vessels as a way of segueing into working on underwater vehicles. He started running diving operations, and eventually started working with the Triton, who build luxury subs.

Caladan Oceanic was a client of Triton, I was working as a design and integration engineer. I worked with Caladan integrating the new sub for their expeditions, and ended up working directly for Caladan on the ship for their Five Deeps expedition as the sub pilot.”

The freedom to explore

The impetus for Tim and Rob’s record-breaking dive came when Cladan wanted to continue the operation with their own sub team.

“Caladan essentially gave me and Rob the freedom to explore the Mariana Trench, with just the ship’s crew for support. That's how the trip was planned. I was primarily responsible for the running of the ship, getting the winches, and the launch and recovery systems set up, and managing storage and oxygen systems."

The sub that was used for the dive, Tim was directly involved in the project, contributing small component design and testing the systems on board.

“We built a pressure chamber in Barcelona, so I spent 4 months there running the pressure chamber. The sub is commercially certified, so it's completely different to any other subs in the world. That was a big design difference. There was a lot of testing involved, as we had to validate that every single component that was going to be exposed to pressure was electrically and pressure tested.”

The expedition was a chance to test the capabilities of the sub's sea acoustic tracking. 

"We use sound waves to measure the distance between assets,” explains Tim. “On the surface we know where the ships are, but we can't predict with accuracy where the underwater vehicles are. We send sound waves out and it will tell us how far away all these assets are, and using that information we can triangulate their location. We are testing how accurate this method of tracking is. It is a complicated process.”

Planning for every scenario

A crucial part of the dive was ensuring that every safety scenario was planned for. A simulator was built to practice every emergency procedure. 

“We have standard operating procedures written down that include little prompt cards akin to what astronauts have. If anything was to go wrong we could pull out these little prompt cards and follow the procedure. In reality, we know the procedures by heart.”

“We have to maintain our own atmosphere so we have to add our own oxygen and we have to scrub out carbon dioxide, if we don't get that right we can have a contaminated atmosphere. We run through scenarios where we have to deal with loss of power, or communication system failure, or what to do if we have a fire. The simulator is set up so that control can set off different alarms and shut off different switches to cause faults in different systems.”

Letting it sink in

Tim says the impact of his individual accomplishment took a while to set in, after being preoccupied with being involved in the operation, looking after all the nitty-gritty details and long days.

“By the time you get in the sub you haven't had a chance to think about what you're about to do,” recounts Tim about the day of the dive.

“It is a strange feeling to slowly descend into what seems like a completely different world. When you take the time to think about it, it is quite daunting. In a submersible you are a little bit removed from it, you have three small viewports, and on the way down you keep the lights off.

“When you hit the sea floor after a four-hour descent and you finally turn the lights on, that's when you realise where you are and what you are doing. When you are at the edge of these huge basins the environment gets really dynamic. You see really big cliff faces, rocky outcrops and underwater dunes of rolling sediment.

“I have only now got a chance to decompress and reflect on what we did and what we achieved in the last year or so. It is cool to see how interested everyone is. It's a nice feeling.”

The reverse space race

The race to the bottom is now on. In the marine science field, there is a renewed push to further explore the hadal zone, the deepest region of the ocean found from a depth of around 6,000 to 11,000 metres.

An estimated 98 percent of the world's oceans are no deeper than 6,000 metres, and is generally the limit of most ocean exploration. 

“There are very few organisations operating below 6000 metres. Most of the time that is for purely financial reasons,” says Tim. “That thinking is slowly changing, and this sub is a testament to that. The undiscovered 2 percent contributes to a lot of the unknown because the difference in biodiversity and geology is astounding. There is a lot of missing information in those trenches.”

In the past three Caladan Oceanic has mapped around a million square-kilometres of the ocean floor and has dived the deepest trench in every ocean. 

The expedition will now explore trenches in the South Pacific, then head to South America exploring the Kuril–Kamchatka Trench, and back to the Western Pacific in the Philippines exploring the ring of fire. 

“Being out on the water is such an enriching experience,” says Tim. “I am fortunate that my job allows me to connect with the ocean, above and below the water. It's special that I can work in the field of marine science and use my skill set to further the knowledge gathering in the scientific community.”