Ski round the loch then swim in it.
Wasn't as bad as I had expected - cold hands and cold back/bum from the zip leakage, but feet toasty and most of rest of body OK. Didn't feel too bad on leaving water- ran back to car parked in lay-by - helped to get warm.
Can't be that cold up there: you'd have to break the ice to swim in the reservoirs around here! Being nuts would also help ;-)
There is fair bit of ice on the lochs - thats why I left it till the last possible day to go for my February swim... didn't fancy the river again.
Nuts have nothing to do with - especially after 10 mins in 0C water ;-~)