Snuba - Stingray City?

[Tex Gal]

I have booked and excursion through Carnival (I am a first time cruiser - playing it safe:) ) doing the Stingray City Snuba. I have done a search and read other people's reviews of this excursion and I have a friend who did it and highly recommended it. Here are my questions:

 

How long do you ACTUALLY Snuba? The excursion is from 12:15 - 2:15 and I am assuming that includes pick-up, training, and departure times.

 

Also, do you spend most of your time swimming or are you just shuffling along the bottom?

 

Thanks for your help! ~ Tex Gal :)