Lens

I have a nauticam housing, canon 80d camera.  Right now I have some with a super wide angle lens, and a 100mm macro lens.   I have found I enjoy the macro (not super macro), stuff far more than wide angle.  

Would the WACP be a good compromise in the middle?  If so, what lens would you suggest to put behind it? 

Thanks!

Which wide lens do you have now  and what (and where) do you want to shoot with any new lens?  Fish portraits?  wide angle scenics, divers on the reef??

The WACP has specific requirements being 28mm equivalent focal length at widest and f3.5 or slower max aperture to work.  The port charts are here: 

https://drive.google.com/file/d/1q81PhYG0_Jdww4I6lycnwBoB_EOFEm8M/view

Anything wider than 18mm needs to to zoom into 18mm to avoid vignetting.