Use 'g' anf 'G' to load a water-tight mesh.
Keep 'x' pressed and click on a pixel to define a ray from the eye that hits the mesh twice.
Keepo 'i' pressed then click and drag the mouse left or right to adjust the radius of the hole.
Press 'k' to close the hole by adding triangles around the cylinder. (This only works if there are exactly 2 border loops.)
'S' will smooth the resulting mesh.