Dean was presented with his medal at an awards ceremony in London which recognised the courage and bravery of 94 people across the country.
In May 2015, Eyemouth RNLI lifeboat crew responded to an incident at the harbour where a man had lost his footing and fallen into the water.
Dean was the first on the scene, and when he saw a man floating face down in the harbour, he jumped in after being told by witnesses that the man had been in the water for between 25 and 30 minutes.
Dean swam to the man and took him safely to the harbour wall, where others helped get him out of the water.
The casualty was breathing, but his body temperature had dropped significantly.
Paramedics then took him to hospital, where he made a full recovery.
Dean said: “When I saw that the man was floating face down in the water, I knew that I had to act quickly.
“All my RNLI training kicked in, and I did what any of the other crew would have done.”
Inspector Bryan Burns, of Police Scotland, said at the time: “Thanks to the efforts of Dean Mark, a young man was saved from what was potentially a fatal situation.
“It is through his selflessness and bravery that this incident reached a positive conclusion, and Police Scotland commends Dean for his swift action.”
Dean’s bravery was recognised at a Police Scotland awards ceremony last year for the same rescue, and in October this year he received another award at the [email protected] 2016 ceremony from First Minister Nicola Sturgeon at Edinburgh Castle.