I dont know if this will help, but I take my 3 under 5 mindees swimming every week.
I originally put his (tongue in cheek) in the CM Staff Room, hope it helps.
We can take two children per adult swimming
So usually I have a adult helper (Little Cook, Big Cook????)
Anyway, I have a friend who is CRB cleared, she brings her little girl and I pay for her to get in.
OK are you ready for the masterclass.
Before you go, change all kids into all in one fleeces, and vest and nappies.
When you get there, change yourself first, then eldest and so on down the line, as you take the clothes off, hang on peg the way you are going to put them back on, with nappy over the top.
Once in water, all have arm bands and rubber rings, that way you can keep them all above the water level and grab them by the ring, if they float to far away. Never Ever put child in ring without armbands they can slip through.
Once swimming is over, strip child, sit on floor (they will fall off benches) with bum in the ring, (they cant crawl off then) cover with towelling poncho so warm and give snack and drink.
Dress yourself, you cannot dress them if you are cold and shivering, it takes twice as long.
Then start with the youngest usually they are dry by this time, dress, put in buggy cover with blanket, do the next child.
I can usually get us out and all 4 of us changed and in the car in 15 minutes.
Then straight home to bed, if they make it that far before falling asleep.
So endeth the masterclass