Unpolished video about the engineering behind choosing a camera lens for your bath

This crappy vid was done in one take. I hope to do a MUCH better version in the next few weeks. Hopefully.
If you are going to use a DSLR I have a great guide at gr5.org/bath but if you want a ras pi camera or some custom camera solution then you need to understand about what is important when choosing a camera lens for a bath.