We live a few hundred yards from a dairy farm, and there are quite a few of them about.
I keep an eye out for them in the summer, and as you say, they are quite slow, so are easy to splat if they land on you.
My wife also swears by the little electric click thingy to relieve bite itches, I dont normally bother as mozzies and midges either dont bite me, or i dont react
As you say out on the water you dont get a lot of problems unless you are real close to shore