Any USM EF lens can be over ridden using the MF ring on the lens. I use this method using my Aquatica housing. I have the AF/MF Macro port. If I want to use MF, then I turn the external knob on the port body, this is in turn connected to the MF gear mounted on the lens. I have back button AF enabled so if I want to use the manually focused image then simply triggering the shutter release works. If I want to go back to AF then simply re-engaging the rear AF button starts the camera to AF. Aquatica also has a MF port extension for use with the Canon 16-35/17-40L Wide Angle zooms.