Wow this is from ages ago... I wonder if Raks got rid of him... I hope so!
I've got rid of boyfriends for much less than that!!
Definitely don't do it. Your training is done! I've done a few marathons... all you can do is harm at this point!
If you are worried about weevers you just need some aqua shoes/wetsuit boots or something to walk into the lake. You could even use cheap waterproof sandals and chuck them back to land once you're in!
It will probably be fine though - I bet most people will go in with bare feet.
Have you been to a doctor? It could be a stress fracture - you should get it checked out.
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