You need a boat to dredge; any boat will do, there is no specific "Dredger" boat type. When not in a boat, you can only dredge to the same depth as you could dig with a shovel, which is 2 dirt deep below water level.
To dredge, embark on drive a boatto +-corner you wish to dredge and disembark, move on top of drag the tile boat to corner you want to dredgeand stand still for a few seconds, embark the boat, activate the dredge, right-click the boat or the tiles below, and select "Dredge". Boarding the boat as a passenger may help you stay on top of the tile easier, without drifting. Dredging makes the tile you dredged steeper, just like normal digging.
==Digging for Rock Guide==
==Tutorials==
* [[Visual digging with Axeblade]] a in game image guide to flattening 2 tiles