Clay Dirt
Clay Dirt is a block found in the Overworld underwater or on the banks of bodies of water. It uses the same texture on all six sides of the block. Clay Dirt is generated commonly in swamps and due to the shallow depth of water in swamps, is the most accessible source of Clay.
This can be harvested by hand to produce 1 Clay Pile. It can also be harvested using a shovel to produce 1 Clay.