Australian troops and members of the US marine corps have honed their skills today in the warm waters off Fiji.

From the air, land and sea, the naval might of Australia was on display with the humanitarian assistance disaster relief (HADR) exercise; part of one of the most significant tours of the South Pacific.

The visit to the region by the Australian Defence Force (ADF) is to strengthen security and partnerships.

As China becomes increasingly active around the waters surrounding the Pacific islands, Australia is responding through development assistance, defence cooperation and emergency disaster response.

About 300 Australian troops were joined by the Fijian military and backed-up by our greatest ally in the form of almost 50 US marines.

They've embedded on HMAS Adelaide, a show of force and friendship.

“It's great to strengthen those ties and show American faces on the little islands around Australia,” First Lieutenant Lou Caraglia of the US marine corps told 9NEWS.

“It’s very important especially with Fiji being an island nation,” Second Lieutenant Jerome Taoi from the Fijian military added.

Athleticism, precision and naval know-how were also front and centre, along with world class techniques used in cyclones, tsunamis, earthquakes- the same prowess also needed for combat operations.

“It’s very important that we keep this skill happening. we've got this fantastic capability to so much for so many nations in our footprint,” POB Matthew Jarvis of HMAS Adelaide said.

This naval tour is undoubtedly a push back. The Australian presence has been prioritised by the federal government, as Beijing continues its push into the South Pacific.

Even now a suspected spy ship has been lingering off the Adelaide in the port of Suva, suspected of gathering intelligence.