Mat 14 mm behind a flat port will give you 77.5 degrees diagonal in water which is short of the minimum 80 degrees you typically want in video
I agree barrel distortion is uncool in video I typically would look at flat ports with a wet lens giving between 80-90 with a preference of course for 90
However flat ports at focal lengths below 35mm give horrible pincushion distortion, this is the reason why they are mostly only used for macro where you are over 60mm
I think you should look more in detail at the theory before making purchases a good link is Flat port theory
I have looked at your vimeo it looks like you have an amphibico housing and a sony?
I agree barrel distortion is uncool in video I typically would look at flat ports with a wet lens giving between 80-90 with a preference of course for 90
However flat ports at focal lengths below 35mm give horrible pincushion distortion, this is the reason why they are mostly only used for macro where you are over 60mm
I think you should look more in detail at the theory before making purchases a good link is Flat port theory
I have looked at your vimeo it looks like you have an amphibico housing and a sony?