Touring the Thames - and history

A ''puny'' 200-mile river, historically and culturally ''the most celebrated body of water in Western civilization,'' is the topic of the final National Geographic Special of the year.

''The Thames'' (PBS, Wednesday, 8-9 p.m., check local listings for premiere and repeats), narrated by Glenda Jackson, meanders like the river it describes, moving on to land here and there, jumping back into the currents of ''Father Thames'' whenever it sees fit. From recording the duties of the royal swan-keeper -- the ''swan-upper'' -- to eavesdropping on the Eton and Oxford student body and the royal family at Windsor, this amiable film portrays the history of the Thames -- and of the area it flows through -- in charming segments.

''The Thames,'' produced by the National Geographic Society and WQED, Pittsburgh, with a grant from Gulf Oil, was written, produced, and directed by Irwin Rosten, a man who obviously loves The River as well as The Island. He finds echoes of past and pleasant glories in every swirl and eddy of the Thames, as he takes viewers on a fabulous journey through British past and present.

What was once the most polluted river in the world has managed to clean itself up. Today it's the cleanest metropolitan estuary in the world. Nearly 100 species of fish have returned to a river which, during the mid-19th century, had become an open sewer.

''The Thames'' is required viewing for Anglophiles with the echo of Bow bells in their ears. Seeing it is second only to a leisurely excursion on the Thames in a punt.