The rescue sub can operate in depths of up to 300 metres.
The world's most advanced rescue submarine, commissioned by the Chinese Navy, is undergoing trials at an underwater centre in Fort William.
Capable of operating in depths of more than 300 metres, its size means it can rescue up to 18 people at once.
The trials are taking place in Loch Linnhe, where water depths are up to 150 metres.
The vessel could deal with incidents such as Russia's Kursk disaster 2000, in which 118 sailors died.
Once the first phase of tests are completed, the LR7 will take part in a simulated rescue.
The final phase of trials, part of an extensive testing and design process, will include pilot training.
The vessel was designed and developed by Perry Slingsby Systems, part of the Aberdeen-based Triton Group.
Underwater tour of the rescue sub
BBC reporter Ben Geoghan described the experience of going down in the submarine as "quite comfortable". He said the main advantage of the LR7 is its large size.
He added: "There is, what someone described to me, as something of an underwater space race going on. One which presumably the Chinese now are leading, but the Koreans and Singaporeans are not far behind.
"The real test will come when we do get another accident at sea involving a sub to see which vessel is deployed and whether they do manage to bring back survivors."
The rescue submarine itself has a relatively quick turnaround time and can stay underwater for up to four days.
Martin Anderson, chief executive of Triton Group, said it was an "extremely exciting development".
After the trial is complete, the LR7 will undergo further checks and be fitted with ancillary equipment before being delivered to China for sea trials.
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