Submarines have two internal Russian names, usually the name of a fish
(e.g., Akula, Kalmar, etc.) and the "project number" (in this case, the
Russian word "project" is close to the English "type"), such as Project
941 or Project 667. Variations within each type differ by letters attached
to the project number, such as 667 BDRM. In addition, submarines are given
reporting names by the US and NATO.