"Can I adjust the focus manually?"
All SEACAM silver housings feature this possibility as standard. For the adjusting the manual focus different gears are necessary just like with the zoom lenses. Basically all lenses work with a very efficient auto focus system so that you can do without manual focus adjustment. For macro lenses with long focal distances and respective objects poor in contrast the manual adjustment can be much more efficient. Also in the wide angle area, especially with over&under images a manual focusing is indispensable. When mounting focus gears you proceed just like with zoom gears. The distance to the zoom gear ring should be 1mm.