need HELP please!

[shoolover]

We are cruising in April/May to Hawaii and would like to book a snorkling excursion but our dilema is that the only time we have open to snorkle is in Lahaina Maui which is our overnight port. We booked the atlantis sub for Apr 30 when we get in to port @9:45am (duration is 1 1/2 hours) so we could snorkle in the afternoon. I would book the next morning but we depart @ 1pm and most trips are 5 hours so that won't work. I've read on the boards that there aren't usually snorkling trips in the afternoon because the wind conditions pickup too much but I found this trip online on the Four Winds II Cruise.....has anyone gone on this and are they reputable. Also, does anyone know where the Infinity (Celebrity) comes in to port and the location of Lahaina Harbor (sub adventure) and Maalaea Harbor, slip #80 (Four Winds II). Would we have time to get from harbor to harbor? This is our first time to Hawaii so we're lost!!! Any info will be appreciated!!