Which lens for the A7SIII

Hello all
I need your advice regarding lens for the A7SIII. I have ordered the Nauticam and it should arrive next week. I mainly want to film underwater. But I am still unsure which lens and port solution to start with. First I wanted to start with my 28-60 and later buy the WWL-1. With this solution, however, I think:
- I need zoomgear
- I actually need the WWL-1 at the beginning because of the 28 mm.
- The lens is not really fast
- I think I have never used a zoom over water when filming
I have now stumbled upon the 24 mm G. My thoughts on it:
- the port solution is cheaper
- the WWL-C is cheaper
- the lens is faster
- I don't really need the zoom
What do you think about this solution? I want to capture the reef as a whole, not spend too much and I should be able to travel with it.

Thanks for your advice

24mm in UW terms  is not wide, working UW is somewhat different to land based shooting, you use wide angle lenses not so much for field of view but to get closer to subjects.  Also concepts like speed of lenses are different.  In general terms rectilinear lenses in a regular dome need to be stopped down to bring the corners in.  The WWL will allow you to shoot at wider apertures maybe the f4-5.6 range.  I assume you realise the 24 or 28mm lens through the flat port will have quite poor image quality so really as you said you need the WWL from the start, unless you want to use the longer focal lengths for fish portraits and the like.

I assume you are talking about the 24mm f2.8G lens?  I would think that purely filming with the 24mm/WWL-C would be a little limiting.  It is the equivalent of of approximately a 10mm rectilinear lens so everything will be very small in the frame and there will probably be many times when you might want to zoom in a little to highlight some activity on the reef- maybe that big school of fish is not quite close enough or you find some interesting behaviour to capture or perhaps a shark swims past but not close enough for your 130° field.  

Thank you for your reply. I was just thinking that it will be difficult to keep still at 60 mm anyway?! The question is simply which is the best solution without having to buy an expensive and large dome port. So you don't think I could start with the 24 mm at the beginning without WWL-C? 
(yes, I mean the 24 mm G...)

You could and you'd get photos but especially at the edges you would have softness and a lot of chromatic abberation and because the filed of view is narrow you will probably be further away from your subject so more water between you and the subject which will degrade the image.  You get about a 1.3x magnification from the flat port as well so a field of view of a 30mm full frame lens more or less.  It's not wide, not macro , max magnification is only 0.13x so you can get closer to increase subject size in the frame.  I don't believe you'll have problems keeping still at 60mm,  you have in body stabilisation which is quite effective. 

Of course all this applies to the 28mm as well but once you zoom in to around 30-40mm the picture quality will improve - of course you can only take fish and larger creatures and small segment of the reef until you get the WWL.  From all reports you won't get any great image quality advantage with the prime over the zoom and I still believe there will be good uses for the zoom.  Neither lens is what you would use alone without the WWL for wide angle reef shots.

So would you say for the reef scene as a whole I need either the 28-60 compelling with WWL-1 or then a proper wide angle with large dome port?

Either will work, the 28-60 behind the WWL is wider than any rectilinear lens and more portable, the widest Sony lens in rectilinear is the 12-24 and you are looking at 10mm equivalent with the WWL.   But the 12-24 and 16-35 you would want a 230mm dome which is big expensive and difficult to travel with.

If you were purely doing stills the lens of choice would be fisheye, but they are not popular for video, mainly I think because you need to watch what you put in the corners as they are distorted and for example a fish swimming through the frame would start out skinny and stretched and get fat in mid frame.

But you primarily are looking at video so the widest lens is the WWL and gives you a 10-22mm equivalent lens.  I think you will find the 10mm works well in some shots, but you may want to use the other end of the range for example to get the fish on the reef bigger in frame.

Thank you so much Chris. So the case is clear for me and I start with 28-60 + WWL-1. Always knowing that other lenses and ports will come later :-)

Curious if you pulled the trigger and bought this? I'm following in your footsteps but haven't ordered the Nauticam stuff yet. I'd love to hear more if you've tried yours? I have my A7Siii though and use it daily. Can't wait to take it underwater!