The ACR Firefly Pro Waterbug — a water-activated LED rescue strobe built to marine survival standards.

This is the step up from the C-Strobe: brighter, built tougher, and it turns itself on in water rather than waiting for someone to find the switch.

The LED means long run time from the battery and no filament to break on impact — which matters for a device whose whole job happens after something has gone badly wrong.

Used on lifejackets, in ditch bags and on offshore gear. On land it is a night marker that outperforms anything else you could clip to a pack.

A hundred dollars buys equipment designed on the assumption that it will be used exactly once, in the dark, by someone having the worst day of their life.