Sorry to hear your CA plans did not work out. There is a thread open with initial plans to go out to CA sometime between June and October! Not sure how that will play out, but CA Kelp diving and/or some shore diving at Catalina is something I'm very interested in doing this year.
This may sound like a foolish suggestion, but have you checked to see if your camera LCD has a brightness adjustment? However I'm guessing the reason the screen is dark is that there is not enough light? Unfortunately bumping up the ISO will result in noise, and likely not very acceptable at ISO 400, but I have not done much research on the camera you are using.
As to why the screen then grows bright, that is a bit of a mystery. What are your settings? Does this camera have any manual adjustment at all? It could be that you are shooting in some shutter priority setting, and there aperture can't stop down far enough. Most of the PnS variety have an min aperture setting of f8, IOW's not much.
I'm planning on attending the Shark Bait club meeting tomorrow.If you want, bring the camera, flash, and manual with you, and we can take a look. It *might* be an operator error, but it also may be that you need to shoot in a different mode, I'm thinking aperture or shutter priority or whatever they have decided to name those modes for your camera. Shooting in Aperture mode may solve the issue, but you may also get unacceptably slow shutter speeds. RU using your flash? Unfortunately you really need just manual settings for flash photography, but I'm fairly sure your camera does not support that.
So what was the vis, and the PH of the water like at the Hole? Something sure changed there coinciding with the dredging, but difficult to say if it is related. I continue to get a white residue on gear after diving there, or at least I did in Feb, and December.
Cool that you saw the Piranha. I'm surprised you have not seen it before. There was two, but I have not seen two for some time, so maybe one is Dad food, and lying at the bottom!
Were you able to hook up with Kent? Does not sound like it.