Kind off.
I couldn’t follow your suggestion and create few control point along water edge and set fix Z value for them as it took me about 5 hours to collect all images and water level change because of the tide.
But I was able to follow Zuzana’s suggestion and I managed to change Prior calibration and Lens Distortion parameters. It actually helps a bit, gives me more ‘flat’ surface but it’s still not perfect. Definitely proper ground control point are welcome on this kind of work.
Thank you guys for all your suggestions.