VERY simple light ideas?

[junior diver]

I'd like to make a simple light just for a back-up, I have made one for a primary night dive light but that is just too big for a back-up, any ideas? Oh, some details would be that it would be for a maximum of 75ft and in salt and fresh water.

 

[DeepTrip]

In my opinion, you'd better buy rather than DIY for backup light. I bought my backup light for less than $10.

In case you insist, the Air Speed Press book have some simple plan to make small dive light, which I think quite suitable for backup.

Benny