I'm installing a system like this [url=http://www.kayakfishingstuff.com/articles_view.asp?Kayak_Articles=54:b6d77]anchor system[/url:b6d77] on my kayak. Basically it's a loop of rope from bow to stern, just above the water line.

You put the anchor through a carbiner and move the contact point to the bow or stern, then secure the anchor line on a cleat by where you sit.