This is the shape of a SL4 ( 4 C batteries) UK light.
The bulb is blue and not purple. This is an ultra violet light, according to the packaging, but it does not perform like an ultra violet light. I tried it on my passport and it did not glow the way a purple light makes it glow.
If you are looking at this light them you know the purpose of a blue light underwater.
UV455 Blue 3 W Depth 500 ft
