Anchor knot.

 
  I tried the 1.5lb grapple anchor  (Like the one pictured) that came with my original OB, (Part of the fisherman's package then) while on Loch Lomond when we were able to use the lake, the small anchor would not hold while I trying to stay put in one of the coves for bluegill.  I added a about a 1.5' of chain and still it was too light.
  Got a 5lb "Danforth" with same length of chain and it hold me firm now.  Course this was on a lake, no current or moving water! Oh and 50' of paracord.

Thanks for all of your tips on anchoring. I'll experiment and see what works best for me.