Question Macro and focus types

[Barmaglot]

+1 for water contact optics. You might need to be willing to use the 16-50 or the 30mm 3.5, but pop the 67mm threaded macro port on if you have it, then add a nauticam cmc-1? Not the cheapest, but more flexible maybe?

I tried the 16-50mm with the short macro port (not the one @Craine has; the shorter one) and Weefine WFL05S and found it a bit too limiting. CMC-1 is similar in strength, so I don't think it'd be a good choice unless you're after the really small stuff. Something in the +5~7 range would be better as a primary, with a +10~15 as backup for when you find something tiny.

30mm f/3.5 won't gain anything from a close-up lens; it already focuses right down to the port glass. Diopters are not like teleconverters, they don't reduce your angle of view, they just let you get closer to the subject.