Celebrity Catamaran Cost Variations

In my cruise planner, there are two catamaran snokle excursions that I am interested in. One is 3h15m for $50 and says it goes to two snorkle spots, with a beach and rum punch after. The other has the same description, also $50, but says 4h long. Any idea why? We are obviously planning to book the 4 hour one....

The 4 hour tour may be further away from the cruise dock so the difference is probably travel time to and from the excursion boat.