This name is a synonym of Najas marina var. intermedia (Wolfg. ex Gorski) Rendle.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 22200032) with original publication details: Fl. Brandenburg 1: 670 1864.
This name record (from Tropicos) was not included in version 1 of The Plant List. It is possible the same name was included from a different data source, to check this you can search for Najas marina in version 1 of The Plant List.