It's going to get cheaper to go under the sea.

Atlantis Submarines, which operates under submarine tours off three Islands, has announced special kama'aina fares for its sub journeys as well as dinner cruise tours in celebration of the company's 20th anniversary, now under way.

Atlantis will continue to offer Hawaii residents the special rate of $20 for adults and $10 for children (ages 12 and under) for its submarine tours off Waikiki, Lahaina and Kona through the end of September.

From October 1 through December 31, kama'aina rates will be $37.70 adults and $16.16 children for the standard sub tour, $49.55 and $33.39 for a premium sub tour, reflecting savings of up to more than 60 percent of regular fees.

In addition, now through the end of 2008, Hawai'i residents can save 20 percent off the regular price for Atlantis Cruises' sunset dinner cruises and more than 40 percent for a combination submarine and dinner cruise package.

"We want to say mahalo to the people of Hawai'i for 20 years of support in helping to make Atlantis Submarines a world-class tour experience for enjoying the beauty of our marine environment," said Ronald Williams, president and CEO of Atlantis Submarines.

Atlantis launched its first sub dive site off Kona in 1988 and three years later added dive sites off Waikiki and Lahaina. Guests descend to depths of 125 feet aboard the world's most technologically advanced passenger submarine in an air-conditioned cabin allowing personal viewing portals to see Hawai'i marine life. In Honolulu, sub cruises depart from a pier off the Hilton Hawaiian Village.

Atlantis Cruises depart at 5:15 p.m. from Aloha Tower Marketplace for a two-hour sunset cruise aboard a 140-foot vessel, called Navatek I, which accommodates more than 300 guests and features outdoor upper and lower observation decks, and two air-conditioned dining rooms with large picture windows. There also is entertainment aboard, plus from-the-sea vistas of Diamond Head and the Waikiki landscape.

Information: 800-548-6262.