An Atlantis Submarine Tour does not require a full day or even a half-day like many other activities. If you schedule you tour early in the morning or late in the afternoon, you have most of the day left to do other things or just relax on the beach.
Discounts from the book rate are widely available in many of the free publications you'll find on Maui. You can pre-book on the Atlantis Adventures website and receive a 10% discount. Combined adventures with luau, helicopter ride or whale watch cruise are available as well. A Maui Passort is also available which includes admission to five top attractions on Maui for one low price. Guests receive an Atlantis Submarine Adventure, admissions to the Maui Ocean Center, Maui Tropical Plantation, Hawaii Nature Center and the Maui Golf & Sports Park.
The best place to check for current pricing and combination tours is the Atlantis Adventures website.