As the first light of dawn broke over the waves off Australia's east coast, the crew of HMAS Stalwart were already hard at work.
The deck buzzed with energy as sailors double-checked gear, ran through procedures and gathered in small groups to review safety measures.
For boatswain's mate Able Seaman April Matthysz Hamblin, the morning brought nerves and excitement in equal measure.
"There's a real sense of purpose on these mornings," she said.
"Everyone knows how much we rely on each other to do this safely and smoothly."
A replenishment at sea (RAS) is when one ship transfers supplies such as fuel, water, food and ammunition to another ship while both are moving, usually at a great distance from the nearest port.
This process is crucial because it allows naval vessels to stay operational for longer periods without needing to return to shore for resupply.
Stalwart recently carried out two separate RAS operations with HMA Ships Arunta and Canberra, while both ships maintained course and speed at sea.
For those unfamiliar with naval terms, this is a bit like refuelling a car from a moving truck while both vehicles hurtle down the highway - only with heavier cargo and higher stakes.
'Everyone knows how much we rely on each other to do this safely and smoothly.'
Conducting a RAS takes more than just technical skill - it demands real teamwork.
Each operation involves 30 to 60 personnel, with all departments working in sync.
Ship handling, line management and the actual transfer of supplies must all happen smoothly and safely.
Boatswain's mate Petty Officer Gabriel Kamung said everyone on board has a role, and they rely on each other's focus.
"There is pride in seeing so many moving parts come together for a successful operation," Petty Officer Kamung said.
"I was also thrilled to find that one of my instructors from earlier in my career, Chief Petty Officer Cameron Ferguson, was part of the team on HMAS Arunta receiving our RAS."
Stalwart is part of Navy's Supply-class auxiliary oiler replenishment fleet - a type of ship designed specifically to carry and deliver supplies out at sea.
In simpler terms, an 'auxiliary oiler replenishment' ship is like a floating service station and supermarket, built to support other naval vessels wherever they are.
Stalwart can carry enough fuel, water and food to keep several ships going for weeks.
Measuring about 174m and weighing 19,500 tonnes, she can reach speeds up to 20 knots (about 37km/h) and travel as far as 11,000km without needing to refuel herself.
She also has space for a helicopter, making it possible to deliver supplies by air if needed.
Behind each successful replenishment is a story of careful planning, constant training and trust between sailors.
'These operations may never make headlines, but they keep our ships at sea and our borders secure.'
Commanding Officer Stalwart Commander Adam Simeoni summed it up.
"The entire crew's dedication ensures we can keep Australia's fleet ready and operational no matter where we're needed," he said.
"These operations may never make headlines, but they keep our ships at sea and our borders secure."
Commanding Officer Arunta Commander Aaron Norley reflected on the activity.
"Commander Simeoni and I were both patrol boat captains at the same time and have been friends for a long time," he said.
"It was special for me to have Stalwart as the first ship I was in company with after taking command and, I believe, the first ship they connected up to after coming back from repairs.
"Replenishment operations are some of the most challenging things we do as a Navy. It requires seamless coordination between both ships' bridge teams, line handlers and engineers.
"It is a truly whole ship evolution and practically trains technical skills that just can't be simulated.
"Having Stalwart back on the line is amazing to see. She is a force multiplier keeping us at sea and on mission longer and further from home. Being able to work and train with Stalwart makes us all better mariners."
Commander Australian Fleet Rear Admiral Chris Smith reflected on the broader impact of replenishment ships within Navy.
"Tankers such as Stalwart are key enablers of our maritime operations," Rear Admiral Smith said.
"By extending the reach and endurance of our fleet, they allow our warships to remain on station, protect vital interests and respond rapidly to emerging threats - wherever and whenever required.
"Without the critical support provided by our auxiliary oiler replenishment ships, sustained naval presence and operational flexibility would simply not be possible. They are, quite literally, the lifeline of the fleet."
