Advice to help my autistic son with swimming

Here are a few things I found when learning to swim that might also be affecting your son;

The main thing that made me quit swimming lessons (though I would still swim in an informal environment and became a fairly adept self-taught swimmer) was that I struggled understanding the teacher due to the sound disturbances that came with using the pool. 
A. The voice of the teacher was distorted and echoed by the tiled walls/floor and the water's surface, rendering it very hard to distinguish and understand. 
B. The splashing of the water around me and noise of other people using the pool further prevented me from hearing instructions (I am very sensitive to sound, so even if it wasn't even audible to the other children the splashes, plops and drips would absolutely drive me bonkers. I also lack the ability to filter relevant sounds from background noise).
C. The teacher would often issue instructions from a distance, being outside the pool, which didn't help with the filtering aspect
This basically rendered every swimming lesson a frustrating battle to understand and apply what I was being asked to do. I could just about manage it through the basic lessons, but when I advanced to a class taught by a teacher with a noticeable accent it became too difficult to the point that every instruction was literally incomprehensible.

Also, I have always absolutely loathed the feeling of water in my ears. I end up acting like a cat with a flea in its ear, literally thrashing my head about because the sensation is so unbearable. I now use earplugs or my waterproof MP3 player when swimming and am perfectly fine.
I also use a noseplug and goggles because I hate water in my nose and eyes too. This also helps avoid problems with the feeling of pressure being uncomfortable in my case, which was mentioned as a possible issue by Graham.

Oh, speaking of goggles, chlorine might be an issue too. I was always very sensitive to it in my eyes and the smell isn't pleasant either (smells are another of my sensory hypersensitivities). 

You might think from reading this that swimming just isn't for me, but as long as everything's plugged up I do love it! It's my main and favourite form of exercise. :D I especially love swimming in the open sea- no chlorine, the salt makes me pleasingly buoyant and the sound of actual waves is quite pleasant! It's just unfortunate that you have to suffer the pool to get there...

One of my problems was the chlorine. I hated going under because it got in nose and mouth (and I'm sure I could even feel it in ears), and it feels like choking for ten minutes afterwards. I also never really saw the positive attraction of the sensation of swimming or being in the water. My other obstacle may have been a genuine problem with buoyancy, that was exaggerated in my mind, so I found it hard to let go of the side. I was pretty much OK in the pool in primary school with a float or one armband, but I was a skinny 11-year-old. People tell you to just lie back, or go into a ball, but if I try that my head goes under, and I panicked, which is itself an aversive experience. So I had one or two 'lessons' that I couldn't cope with. Fortunately I was never thrown in.

The solution to both the problems was the sea. I can't really swim a length still and wouldn't go alone, but as an adult with rather more normal BMI, I can hold my head above water enough, and if it does go below at the wrong time, it's only brine.

I'm not an expert on this. Is there any reason slow 'graduated exposure' shouldn't help autistic people be less anxious about situations? Do a bit beyond what's comfortable, but not too much, several times until it's familiar. Then go a bit further: hold your head under the water for 5 seconds with goggles until OK with that, and so on.... The other thing presumably is for someone to explain exactly what will happen and what is required of you beforehand. Are there 'social stories' relevant to this?

One of my problems was the chlorine. I hated going under because it got in nose and mouth (and I'm sure I could even feel it in ears), and it feels like choking for ten minutes afterwards. I also never really saw the positive attraction of the sensation of swimming or being in the water. My other obstacle may have been a genuine problem with buoyancy, that was exaggerated in my mind, so I found it hard to let go of the side. I was pretty much OK in the pool in primary school with a float or one armband, but I was a skinny 11-year-old. People tell you to just lie back, or go into a ball, but if I try that my head goes under, and I panicked, which is itself an aversive experience. So I had one or two 'lessons' that I couldn't cope with. Fortunately I was never thrown in.

The solution to both the problems was the sea. I can't really swim a length still and wouldn't go alone, but as an adult with rather more normal BMI, I can hold my head above water enough, and if it does go below at the wrong time, it's only brine.

I'm not an expert on this. Is there any reason slow 'graduated exposure' shouldn't help autistic people be less anxious about situations? Do a bit beyond what's comfortable, but not too much, several times until it's familiar. Then go a bit further: hold your head under the water for 5 seconds with goggles until OK with that, and so on.... The other thing presumably is for someone to explain exactly what will happen and what is required of you beforehand. Are there 'social stories' relevant to this?

*nod* Good ideas, Cassandro. I think it would have helped me to get instructions outside the pool and then gone in and tried it out, it could well be a decent thing to try for this child esp. if they have one-on-one (so the teacher actually has the flexibility to do that).

The sea is definitely the best place to swim.