With several of the largest, flashiest cruise ships ever designed making their debuts over the next few years, cruise lines are investing in their older ships to keep them competitive.

Crystal and Princess each recently spent millions of dollars upgrading older vessels, as competitors in their respective categories debut new ships, such as Celebrity's Solstice-class vessels and Seabourn's three Odyssey-class ships.

The $25 million makeover of the Crystal Symphony included new pool deck furniture; a reworked Lido restaurant with service islands replacing the buffet; newly designed specialty restaurants; and upgraded penthouse accommodations.

Crystal has not taken delivery of a new ship since the Crystal Serenity in 2003, and the Symphony is 15 years old. The line has continually invested in its two ships and has spent $65 million refurbishing them both over the last three years.

Bill Smith, Crystal senior vice president of sales, told a group of travel agents visiting the Symphony last week in New York that the investments have kept the ships not only relevant but superior in their categories.

"You can sail on a new ship, or you can sail on the best ship," he told the agents.

From Oct. 9 through 23, the Coral Princess was in drydock at the Grand Bahama Shipyard in Freeport, Bahamas.

Princess would not say exactly what it spent on the Coral Princess. The cruise line upgraded the ship with the Sanctuary, an adults-only, quiet area that has been popular on other Princess ships. It also installed the Movies Under the Stars poolside screen.