@suckypaddler It looks like there are some resources available to you!

I don't do ocean kayaking or anything - nothing crazy serious - but somebody told me years ago to be sure to let each side of the paddle do a full stroke, which meant being sure it made complete contact with the water - not just the tip, but the whole end of the paddle - as far forward (relative to the boat) as possible, and then all the way back. If you can keep this consistent on both sides, these full strokes with the paddle totally submerged, that might help! Just be sure not to move in a way that's a serious strain, because if it's a physical stress to start, it could mean something more difficult a while later.

One thing that I've found myself doing when I get tired is to try to engage my core. I'm not sure if an expert would say that's super helpful, but it's a thought!

Good luck!