[acabtp]

Most fishing sit-ins will have a big enough cockpit that that isn't an issue. I can sit indian style in my Dagger Delta for instance. Some touring and whitewater kayaks have a tighter cockpit fit where that may become a problem.

Either way though, sit in or sit on, when you are paddling, you are always in the same position because you brace yourself in the boat, knees slightly bent, feet pressing on footrests and back against backrest (and thighs against knee braces with a sit in). You will properly adjust this before using the kayak and it should not be uncomfortable for long periods of time. Without a well braced position in the kayak, you end up using your arms instead of your whole upper body and that wastes a large portion of your paddling energy.

Floating around out of brace position there are plenty of ways to move. I am a fan of the "dangling my feet in the water" but not really this time of year.