Chopper Joyflights

I was up at Rhona the other day and a chopper came in banked low around the lake less than 100m off lake surface, then hovered as low as 15-20m off lake surface before buggering off.
A bloke at the lake said it was an army chopper having a bit of fun
Is this legal? Should I report them?
I have some video footage also, they were buzzing around the area all day, at first I assumed it was because of fires in the area, or an EPIRB activation but they weren't fighting any fires, and haven't heard of anyone being pulled out of the area.
Cheers, sbs
A bloke at the lake said it was an army chopper having a bit of fun

Is this legal? Should I report them?
I have some video footage also, they were buzzing around the area all day, at first I assumed it was because of fires in the area, or an EPIRB activation but they weren't fighting any fires, and haven't heard of anyone being pulled out of the area.
Cheers, sbs