@PhotoMax ,
It sounds like you shoot landscape, rather than wildlife, from kayak; because lenses of Olympus Tough series are not long enough for most wildlives. So my comments probably won’t help you much.
I put my micro four thirds camera (Oly E-M1 mk1 with Panasonic 100-300mm f/4-5.6 mk2) into a large leak proof box with locking lips. My camera and lens combo is rain proof but will probably die in submersion (so I don’t do Eskimo rolls when camera is out of dry box).
My camera box stays near my butt inside kayak and is tied to kayak with carabiner clips. I paddle as usual. If I see interesting wildlife or birds, I stop, drop anchor sometimes, take out camera and shoot. Then I put camera back to dry box and continue to paddle.
My two photog/paddler friends have been using bigger (and non-water proof) full frame and APSC sensor cameras in kayak/canoe. They simply strap camera over their neck and don’t even lock it inside a dry box. They have been doing it for years and never lost a camera. They do have camera insurance though.
We have to use bigger sensors, as bird photography usually requires fast shutter speed and sometimes high iso. Many super zoom cameras with smaller sensors don’t work very well for fast animals.
For landscape (which is not that spectacular on water in my area), there is usually enough light and no need to stop motion. I simply use my “water-proof” Pixel 2XL from my pants’ pocket.
Your iPhone should also be waterproof up to a certain depth (10 meters?), assuming rubber seals are intact. If you are a good swimmer wearing a life vest, you can simply carabiner iPhone to your belt and have it near you.
Lens and camera (optical and/or digital) stabilization and kayak anchor may help.
Good fisheye lens does not add much unwanted distortion and can be defish’ed or cropped reasonably well. Simply compose carefully with the fisheye effect in consideration. I personally like fisheye lens for some landscape scenes. GoPro’s lens may not be good enough though.
All photos from this album of mine came from my kayak (PakBoats Quest 135 folder):
https://www.flickr.com/photos/zzffnn/albums/72157679716846108
This kayaker is also an award-winning bird photog (he shoots a full frame Canon 5D mk3): https://www.flickr.com/photos/gseloff/
Here is how another pro photog friend of mine does it: https://www.flickr.com/photos/rrcolejr_photography/albums/72157684554438866