[Shrewcub]

Tim and Jon are both correct. I only used my 450 once in about 6 inches of wet stuff. I worked but I wasn't impressed. For the 451, I added 2 paddles that I made out of roll plastic to the impeller. Hopefully I will get the chance to try it out this year.

Here is a site I found that sells them (not an endorsement, just found it on a search) but also explains the principle fairly well.

http://smllengns.tripod.com/id13.html