Where Walter Christie's submarine work may fit

Walter Christie's little-known submarine work is tentatively connected to early US Navy activity around Robert Coontz after the First World War, while his Smedley Butler work is separated as an amphibious-vehicle project.

Question

Which submarine designs did Walter Christie work on?

Short answer

The tentative lead is early post-First World War work associated with Robert Coontz; Christie's Smedley Butler connection concerned an amphibious vehicle rather than the submarine design.

Notes

The answer is cautious because it recalls a paper rather than consulting it during the stream. Christie's submarine activity is associated with early work around Robert Coontz in roughly the 1917-1920 period. Smedley Butler is also mentioned, but that connection concerned Christie's amphibious tank or vehicle work rather than the submarine project. The answer provides names and a period for further research without presenting the recollection as a settled programme history.