Soil placed in ornamental ponds or for container-grow aquatic plants must be dense and heavy. Making pond soil requires a clean, dense topsoil that's rich in clay. Using well-composted cow manure adds nutrients and an improved texture to soils used in submerged containers.
Search your yard for clay-based soil that has little organic matter in it. Purchase topsoil in bags, if necessary, from a garden center. The heavier and denser the soil, the better.
Put three parts topsoil into a wheelbarrow. Pick out organic matter such as bark or leaf compost that will float in the pond once the soil is submerged.
Add one part well-rotted cow manure to the topsoil. Thoroughly combine the contents of the wheelbarrow with the shovel so there is a consistent blend and texture.
Add water to the mixture if it is overly dry and you cannot judge its density. Slowly add water and mix so you don't inadvertently make the soil into a soupy mess of mud. You want it to be sticky, like warm cookie dough.