acr Firefly 3 Waterbug Strobe Light (H2O Activation) Special water activation feature; unit will turn on when it has been armed and comes in contact wit Conceived as state-of-the-art replacement for famous Firefly forerunners, 4F and 4G. Large sliding switch allows for easy operation by gloved hands. Specially-designed base platform allows unit to stand upright easily. Stainless steel retainer securely attaches removable battery door to case.