I have had a hard time getting my pond dug correctly. the people I have had out to do it had a very hard time because the water flows in so quickly. I was looking at the mini dredge (http://www.piranhapumps.com/mini_dredges.html) and it looks like it is just a trash pump?

The soil in the bottom of my pond is 100% fine sand. Today I took a shovel and pressed it into the sand to see how deep it would go before I hit something hard. I was able to push the entire shovel + 4 foot handle into the sand by just wiggling it back and forth.

What type of equipment would I need to buy / rent to dredge this type of material out of the ground?