[fatlazyless]

For $3.45/bag you can get a 60-lb bag of Quikrete hi-strength concrete mix at Lowe's. Purchased by the pallet the price goes lower by 30%

After placing the unbroken heavy paper sack of concrete under the water, it takes just a day for it to set up with the water seeping through the paper bag. Using it like this is called rip-rap, and you can construct an underwater retainer wall with an interwoven design of 60-lb bags which all "melt" together due to the weight and design to build a sturdy underwater wall.

For $3.45 you can give one bag a test, trial run.

People in Maine have been using this for building small dams and underwater retainer walls for many years. It's the Maine way where they want to get it done without calling in some expensive construction outfit.