WORTH NOTING ON TV

* TUESDAY

Seapower: a Global Journey (PBS, 9-10 p.m.): This new six-part weekly series takes on a vast and potentially amorphous subject - the oceans and their historic impact on mankind - and breaks it down into logical categories that make things easier to assimilate. Commerce, politics, anthropology, science, and other topics are considered both individually and in terms of their interdependence.

Narrated by Leonard Nimoy, the production uses photography, interviews, and, yes, some reenactments to span 3,000 years, several civilizations, and other sweeping aspects of the sea's influence - from sea trade during the Bronze Age to the warships used in the Gulf war.

To get the feel of ships and gain insight into the people who live by the sea, viewers travel on a range of vessels: research ships, trawlers, tankers, a cruise ship, and submarines.

The opening episode, ``Lifeblood,'' begins with early civilizations as it traces the economic dependence of humans on the seas. Threatened oil supplies, how copper trade led to the rise and fall of ancient powers, a trip through the Suez Canal - these and other features are part of the first program's view of this fascinating topic. * WEDNESDAY

Mostly Mozart Festival Opening (PBS, 8-10 p.m., EDT): Here's an agreeable way to spend a summer evening - listening to Mozart and other masters performed by superb musical artists.

Aired live, the opening program in the festival's 28th season focuses on ``themes and variations'': Baritone Thomas Hampson sings arias by Mozart, Haydn, and the sometimes overlooked Gluck. Pianist Shura Cherassky, who's in his 80s, plays Brahms, Chopin, and Tchaikovsky.

Gerard Schwarz, named 1994 Conductor of the Year by Musical America magazine, conducts the Mostly Mozart Orchestra. And Hugh Downs serves as the suave host.

Please check local listings for these programs.