Gasplanning for cavediving is in a full cave course. Of course it does not work on exploration where you don't know what is coming. But a full cave course is for recreational cavediving on caves that are already explored. So maps are most times also available. Your instructor will let you do things like determing the swimming speed in the course. And let you read maps.
You look at the map and cut the tunnels or part of tunnel into sections.
For example, the Ressel in France. Okay, it is a little bit outside what is done in a full cave course as not all agencies allow use of decogases or a stage to go further, or the max depth is over 40m, but this cave is easy to explain. The first 180m has a maximum depth of 10m. Average will be around 9, so 10 is nice to calculate with. You know your swimming speed and then you know how long it will take to reach that 180m. Most divers do it in 12 minutes without current. So 12 minutes at 10m, you need to know your sac or rmv and yes you have the gas needed to swim that 180m.
Then the next part, again 180m, again around 10m depth if you take the T left (I know it is in the last part going to 21 at the second T, but this is a short part and I want to make this example easy. Again 12 minutes, so you know how much gas is needed. Then the cave drops to 30-31m. Let's say this will take a 4 minute swim. So again you know your gasamount needed. Then you are at 'puits 4', 450m in the cave. Depth goes to 46m. And then drops to a max of 53 around 550, but the line is around 48m. So you can say average depth 48m, no need to go to the bottom. You want to reach 550m in the cave. So take the time from around 400 till 550m needed (the 4 minutes on 30m are from the second T at 360 to the start of 'puits 4'). And again you know your gas needed. And then you turn. The amount needed back is normally without current, so exactly the same. Put this all in a decoplanner like Multi deco and you know your deco. There are several options for the gases to be used. Some take ean32 and drop it at the 30m point, and then go further on backgas (drop point ean32 is for most divers the stage drop if you use a stage to go further in the cave). Others start from beginning on backgas and drop oxygen at the entrance (Some divers can do this dive on only 1 twin12 with air/light trimix). Others drop ean80 at the first T.
I let students calculate the dive till 40m depth in 'puits 4' for a dive on the last day of the course, with use of 1 decogas. I use the 550m diveplan as excersize. Some make the dive after the course if they have some extra days left. I don't teach cave to divers that are not allowed to do any deco. The course will be too limited.
I also cannot imagine that you do a full cave course in Florida without any deco cert.
Your instructor will help you to determine swimming speed, reading maps, calculate average depths in parts, etc. And let you make a plan like this.
A link to a map of the first part of the Ressel cave where I talk about:
http://www.photo-sub.com/sites/default/files/recit3.jpg
If you can read the French language, buy the book from Frank Vasseur. It also has examples of planning if you dive solo.
