outofofficebrb
HARRO HUNNAYYY
But if you were me which would you buy ?
I would get a GoPro 3 or 4 used. I don't think you will think that the quality of photos and video will be inferior to the 5 where you would regret your purchase and you would be able to save a chunk and put that money towards your lights, trays, or filters. I don't know what your budget is but if money is not a big deal, go for the 5 but if value is important, go lightly used. A great resource you can check out for accessories for the GoPro (tray and lights) are Sea Life and then Backscatter.com.
If you want to shoot smaller items with greater detail and have closer focus distances, you can also look into a macro attachment. At the very least you will need a red filter for blue water diving or a magenta/rose filter for green water diving.