Ask your husband take a video of you swimming next to the kayak. You can get a disposable camera that takes video, or he can just keep a regular camera in a cooler or a dry bag when he's not using it.
Then get a video of you swimming normally in the pool and compare the two.
After 6 abysmal open water swims in a row, I had a breakthrough this week.
I knew my form was falling apart on the open water swims, but I didn't know what I was doing wrong. I was swimming great with my husband in the kayak or if I had someone swimming next to me. I couldn't catch the problem on video because I would automatically swim better if someone was watching.
I finally had the idea to ask my coach to observe me at the beginning of Masters practice and at the end. I wanted her to tell me where my stroke broke down when I got tired. It turned out that as I got tired, my hand started entering the water too close to my head.
So yesterday, I imagined my recovery arm reaching out to touch the buoy on every stroke. My 5,600-yard open water swim was faster and easier than my 5,000-yard pool swim a few days before.