well, you really need to give some more information. Why is it "constantly under water"? Is it in a flood plain? If so, you may not be legally able to fill it in. Can you put in in some drainage tiles/ditches to get the water to move out faster? Or does it just sit there until it evaporates or soaks into the soil? If it wants to sit there, maybe just make it a pondl. LOL. In any case, if you want to raise it one foot, it would take about 1725 cu yds of dirt or about 70 single trailer semi-loads at 25 yrds/load. Also, don't know what is available in your area.
Here in Michigan, last time I bought fill sand it was about $8/ cu yd delivered. People put signs up around here on their property looking for "clean fill", which means they'll take stuff from excavations and such for "free". That's the way a lot of property gets raised, but it takes a while to get it done. Best way to do it would be to fill it with whatever you can get then put 6" to a foot of topsoil on top.
Next question is: where will the water go AFTER you fill it?Make sure you plan for that or you'll be posting back again with another problem.