Upgraded Apple Watch is waterproof, has GPS

"We started shipping Apple Watch just 18 months ago, and already people all over the world are using it in many aspects of their daily lives," Apple chief executive Tim Cook said at a product launch event in San Francisco.

"But we are just getting started."

Chief operating officer Jeff Williams said the Apple Watch Series 2 would be faster and feature GPS -- which will allow people to gather fitness data during an outdoor workout without need to take a smartphone along.

Apple also unveiled an edition of the watch made in cooperation with sporting goods giant Nike, which Williams called "a watch designed with runners in mind."

Sales figures for the smartwatch are not disclosed by Apple, but surveys show enthusiasm has faded since last year's release.

Apple saw a 56.7 percent year-over-year drop in sales of the device in the past quarter, research firm IDC said.

"Series 2 comes in a wide variety of styles, aluminum, stainless steel and a new material -- ceramic," Williams said.

"It is faster, it is brighter, it is water resistant... We think Apple Watch is the ultimate device for a healthy life.