Susannah, have you tried Shepparton Open water swimming? There's a Facebook page, lovely place to swim and there is coaching in mass starts as well as the odd swimming contest with 'mass' starts.
Failing that you might be able to join the SwimSmooth sessions at Richmond Pool where they also practice mass starts as well as draughting (yes, in swimming as well) techniques, I believe.
To be honest, I'm not sure any 'coaching' will prepare you for the washing machine effect that are mass starts at Ironman events, where it's every (wo)man for themselves!
The difference, I've found, is that open water swimmers are a lot more confident in their ability than Triathletes. The latter seem to think it's better to beat you to a pulp rather than beat you with their swimming technique!! So it tends to be a lot more brutal! Open water swimmers are much more polite!
Crikey! Bring out your dead!! This thread has been buried a while!!
Richard, I used to get cramp in my calves on every longish distance swim I did. I'm now very careful on the lead up to an event to make sure I'm properly hydrated prior to the event. To the extent that I take a sachet of that stuff you're supposed to have after you get the sh1ts! Magnesium tablets also help. I also wear calf guards underneath the wetsuit to add a bit of extra compression to my calves. Having said that I've just done the Henley Bridge to Bridge (14K) on the weekend and forgot my calf guards!! I still took the Dioralyte (sp?) sachet the evening before and a Nuun tablet in water as I went to the start. The only time I got more than a real twinge was getting in and out at the feed stations / locks.
If I feel a twinge coming on I curl my toes back up towards my knees (as if you're stretching the calf). It's like throwing an anchor out whilst your swimming, but at least you're still moving forwards. I generally hardly kick my legs except in the last couple of hundred yards of the swim.
My advice to you would be to get a sports massage and get the masseuse to concentrate specifically on your calves (more than they normally would). It may hurt, but it will do you good! There's obviously a weakness / underlying scar tissue there that you have (I know I have) and the massage may release something to help you, it did/does with me! Also get one of those foam rollers and use it on your calves to keep them supple. Don't stop with the foam roller on your calves either, use it on your ITB's and thighs.