Rachel Cousins, Joe Riley and Carol Craig all have men in the armed forces and decided to do the gruelling challenge together in the name of charity.
Rachel, 33, persuaded the others to get involved after she was touched by a letter from a six-year-old girl who lost her daddy in the Iraq war.
The letter had been laminated and tied to the gates on an archway at the Stonehouse Barracks in Plymouth and the girl described how her daddy had not really gone but had turned into a beautiful butterfly.
'That just really got to me,' said Rachel, of Alvestoke Avenue, Fareham.
'Any of us could lose our husbands or boyfriends and there is nothing that we can do to protect them.
'It really made us think that our boys go and do this day in and day out and we have to support them.'
The determined trio have done various fundraisers for the Help The Heroes charity but nothing seemed big enough.
It was Rachel's husband Rob, who is a colour sergeant in the Royal Marines, who suggested the challenge.
The Royal Marine Commando Challenge involves three miles of assault courses and 13 obstacles – including pitch-black mud tunnels, a pool to go through, a two-metre concrete pipe to squeeze through and a pit full of mud.
Joe, 34, of Alverstoke Avenue, Fareham, says: 'I didn't really know what I was agreeing to until I said yes.'
The mother-of-two, whose husband serves as a chief petty officer at HMS Collingwood, adds: 'Now that we have been doing the training I am looking forward to it.'
The women have been running for an hour three times a week to train over the past few months.
Carol Craig, 31, of St John's Road, Fareham, said: 'We have been friends for years but we have a bit of a competitive streak.'
Carol, whose husband Calum is currently training to be an officer in the navy, adds: 'Whatever happens on the day it is nothing compared to what our men go through.'
For more information or to donate go to www.justgiving.com/
wivesdoitwetanddirty