The 27-year-old couldn't believe his eyes when he clocked the mammoth 6ft 5in mammal standing in the water – and feared it could be preparing to attack beloved dog Dharma.
Jackson, from Freemantle, Perth, had been visiting his grandmother in Margaret River and saw the gargantuan animal on her property at about 11.30am.
He said: "I have been going to that creek since I was a little boy and there have always been kangaroos on the property.
"I was walking my dog and we saw this huge roo standing in the water. I have never seen a kangaroo standing in the water like that, we could just see his head at first, and he was one of the biggest I have ever seen.
"As I ran around him to take a picture he came closer and that was when I realised he was coming right at me and he was really big.
"I am pretty confident around animals but the moment when he started to come out of the water my heart definitely jumped and I decided to take a few steps back.
"He looked to be at least two metres (6ft 5in) tall or taller and must have weighed at least 100 kg (16st).
"He had a really big body and was taller than me. There are a lot of roos at my grandma's place but I have never seen one that muscular before – he was a big macho male.
"I decided to get Dharma out of there as we thought the kangaroo was going to lure him into the water to drown him."
Jackson's Facebook post with his images of the kangaroo's muscular physique quickly went viral, racking up thousands of likes and shares.
Online commenters were quick to point out the animal's impressive bodybuilder-like muscular shoulders, biceps and chest and threatening posture.
After dropping Kelpie Dharma back at his grandmother's house Jackson returned to the creek to see the roo was still there.
Jackson added: "His claws were really big – they were as long as my hand. That for me was even scarier than his muscles, they looked nasty.
"I have never seen a kangaroo be so defensive – it definitely looked like he was puffing his chest muscles up.
"I definitely wouldn't like to take him on in a boxing match."
Ten incredible trips to take in Australia
Ten incredible trips to take in Australia
Walkers heading Down Under can experience one of the world's greatest trails in the Red Centre on a classic Larapinta Trail trekking holiday. Along the trail, you'll witness the dramatic colour changes in the rock formations at Simpsons Gap and Standley Chasm, walk the high ridgelines of the West MacDonnell Ranges for a rare perspective of vast flood plains and razorback rocky outcrops, while sleeping at exclusive design-led wilderness campsites. The entire route is 139 miles and takes two weeks, though you can walk shorter parts of it. World Expeditions has a six-day Classic Larapinta Trek in Comfort holiday which costs £1,560 per person (excluding flights).
Travellers can journey from Sydney to Cairns via Uluru and the Outback with an array of activities thrown in for an Australian adventure trip to remember. Responsible Travel's tailor-made Australian Adventure Holiday includes surf lessons on Bondi Beach, camping under the stars in the Outback, diving or snorkelling on the Great Barrier Reef and fishing lessons in the Daintree Rainforest. You'll also experience hiking, a sunset camel ride, boomerang throwing and a tall ship cruise. The 13-day holidays costs from £2,834 per person (excluding flights).
If you're after a whistle-stop tour of Australia’s best bits, then you'll want to explore the likes of the Great Barrier Reef, Aboriginal culture, Sydney and Uluru. Trafalgar’s Australian Highlights tour is the ideal way to fit everything in to 13 days. You'll visit Australia’s most diverse cities of Sydney and Melbourne, get a taste for life at sea with a trip to the Great Barrier Reef and head inland to Alice Springs to be amazed and delighted by the awe-inspiring scenery and Aboriginal heritage to boot. There are also unforgettable insider moments, such as a private tour of the Sydney Opera House and discovering the meaning of Aboriginal dot painting before creating your own. The holiday costs from £2,795 per person (excluding flights).
With species that can be found nowhere else in the world – the Tasmanian devil for one – Australia's wild island state is a truly unique place for wildlife lovers. On Responsible Travel's tailor-made Tasmania Wildlife Tour, you'll discover far-flung corners of this extraordinarily diverse island. The trip includes stays at little-known properties on land that has been protected by its owners, guardians of nature and accidental eco-warriors for decades. There are also many opportunities to spot Tasmanian devils, quolls, wombats, possums, pademelons, sugar gliders, platypus and the rare white wallabies of Bruny Island. The holiday costs from £799 for five days to £2,775 for 15 days (excluding flights).
Far beyond the cliché of 'shrimps on the barbie', Aussies are an epicurean bunch. Southern Australia is laden with wineries providing first-class vino, as well as fantastic seafood, steak and national favourites. On Trafalgar’s Tastes of Southern Australia holiday, you'll spend 11 days touring the delicious delights of Victoria and southern Australia, taking in the spectacular sights of the Great Ocean Road before chatting with your local Aboriginal guide and learning about bush food. You'll also experience the tastes of an Aussie barbecue, bush tucker, premium wines and sumptuous seafood. The trip costs from £2,495 per person (excluding flights).
For couples looking to experience the ultimate trip to Australia, combining iconic Sydney with the picture-postcard Whitsundays is the best way to experience romance, luxury and unforgettable views. Austravel offers a luxurious trip which takes in a stay at the five-star Shangri-La Hotel Sydney, a hotel that's perfectly placed between the Opera House and the Harbour Bridge, and offers uninterrupted views of the city’s spectacular waterfront. You'll then head to the adults-only resort of qualia, nestled neatly into the northern most tip of Hamilton Island and surrounded by the Great Barrier Reef. Each of the resort's luxurious hillside pavilions boast views of the Whitsundays. The ten-night holiday costs from £3,139 per person (including flights), based on June 2017 departures.
While central and northern Australia’s remote wilderness often comes to mind for those looking for nature, Tasmania provides bountiful opportunities for expeditions into the wild. The untouched beauty of Tasmania’s many national parks and stunning wonders can be admired at Wineglass Bay and the ancient forests of Cradle Mountain National Park, Russell Falls, Tasman’s Arch and Devil’s Kitchen. Trafalgar's Perfect Tasmania holiday is punctuated with opportunities to witness the purple-hued fields of Bridestowe Lavender Estate and sample the 'finest malt whiskey in the world' at Hellyer’s Distillery. The 12-day trip costs from £2,731 per person (excluding flights).
One of the world's great train journeys, the Indian Pacific is a must for rail enthusiasts visiting Australia. It is one of the country’s two trans-continental railways, which traverse the country north to south and east to west, linking one ocean to another. The east to west journey from Sydney to Perth covers 4,352 km and takes three nights to complete, passing through the Blue Mountains, mining towns and the Nullarbor Desert, with stops at Broken Hill, Adelaide and the gold mining town of Kalgoorlie. Freedom Australia offers the Gold Sleeper Service from £1,138 per person.
Families can make the most of the east coast of Australia with a multi-centre trip combining Sydney, the Gold Coast and Brisbane. The kids can be entertained with a day trip to Taronga to meet the local Aussie wildlife at the world-renowned zoo, as well as an abundance of beach activities, including whale watching and surfing. Austravel offers a family holiday that combines a five-night stay at the Cambridge Hotel Sydney with a week at the Mantra Circle on the Gold Coast. The trip ends with two nights at Brisbane Oak Towers, which includes a day at Tangalooma Island Resort for the kids to spot wild bottlenose dolphins while mum and dad relax on the white sands. The two-week holiday costs from £1,695 per adult and £1,499 per child (including flights), based on August 2017 departures.
The world’s most ancient living culture, Australia’s Aboriginal people, has a history spanning at least 50,000 years. Theirs is the oldest story on Earth and by sharing their stories with visitors, they can keep their culture alive. Western Australia offers travellers coastal, urban and outback environments, with a choice of authentic cultural experiences, such as going on guided bushwalks, learning about fascinating legends, visiting cattle stations and playing the didgeridoo in music sessions. Cape Cultural Tours offers guided trips around the tip of Cape Naturaliste, where you can hear local stories and go on a guided bushwalk from AUD$72 (£44). Meanwhile, an APT West Coast Adventure with Austravel takes you from Perth to Darwin over 18 days, combining Kimberley, Aboriginal culture and fascinating wildlife, from £5,295 per person (excluding flights).