Completely unsuitable for sailing
After three years of use with two of these headlamps, I'm happy to see their batteries finally reach the end of their life and to upgrade. There's no red light, the light is far too intense, the lamp gets hot, and to turn it off you have to press the button three times, forcing you to cycle through all the brightness levels and blinding everyone on board. The micro USB port quickly deteriorates, and it no longer charges, or charges poorly, so you often think the headlamp is charged when it isn't at all.
Certainly great for the mountains, but completely unsuitable for the sea.