After looking at Mike Quinn’s photographs I can now see the visible similarities.

I rescanned the original slide and measured the extension tube framer I used to take the image. The horizontal distance of the image taken would be approximately 25 mm. I scaled a grid on the scanned image and came up with a length of just under 5mm. I am not sure how accurate this is I always assumed 1:1 extension tubes produced a life size 35mm image, but the framer is only 27mm across, to small for a 1:1 and to large for a 2:1

Another reason not to ID pictures of things without a specimen in hand ... :-)

John I have received another opinion that it is not Coptotomus but more likely some kind of Hydroporinae I do not know enough about aquatic beetles to even hazard a guess.

you might consider checking out my identification manual for Florida water beetles that can be downloaded via my website < http://home.comcast.net/~johnepler3/index.html >; see page 5.47. Or see THE dytiscid manual by Larson et al. There are some hydroporines (some Hygrotus, Neoporus and Oreodtyes) with somewhat similar vittate patterns on their elytra, but I'm relatively sure this is a Coptotomus. I've seen thousands of them ...

I looked at a few images of Neoporus and Neobidessus they looked close but were just not right. After looking at page 5.47 from what I can tell I would have to agree with you.
Very nice key by the way the images and illustrations clearly highlight differences thank you for making it available.

You did not give a size in your submission, but Neobidessus are TINY and marked differently. As I wrote above, there are other dytiscids with vittate markings, but not like those of Coptotomus. You might inform the giver of your "other opinion" about my manual, too. :-)