The swim, as others have said, is not timed. Any stroke can be used and in any combination. I'm not what anyone would call a fast swimmer. It's not the Olympics and, while I can if need be go quick in an emergency, fast is not really required in diving.
The swims, treading water, and short underwater swim are more about gauging comfort in the water and the ability to be ok around water in general. Drowning is a large cause of death in kids. Because they are allowed around water and never taught to swim. Parents will spend money on dance, tee ball, cheerleading, jr hockey. etc. and while that's not a bad thing, they do that in lieu of swim lessons. Again, not a bad thing if the kids will never be around water deeper than a wading pool. If they are going to have access to water, in my mind, not teaching them how to swim is neglect bordering on endangerment.
Also, in rescue situations, the swim you would use is not the same as one you'd use in a race. In a rescue situation, you need to keep eyes on the victim and so the head underwater race swim doesn't work.
And you also need to have enough left in the tank to assist the victim back to shore or the boat. Arriving winded after a sprint isn't going to be very helpful.
If necessary, we can start each session with several laps just to get you more comfortable and raise your endurance level.
One of the best gifts I ever got was at the age of 56 when my GF got me an hour with a pro swim coach at a local fitness center. I learned to swim at the age of 4 or 5 from my grandfather. Been swimming over 50 years at the time and I learned a lot in that hour.