You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
alternatehistory.com
Would it be possible to put Disappearing_guns on a large submarine moniter, perhaps within a sort of hold and thus avoid the need for it to be above the surface whilst firing and reloading ? I imagine it would be possible to quickly drain a firing room to reload and it would be quicker than surfacing.