The flurb from the site says...
Bring: Torch and stout footwear.
Children: Sorry, not suitable.
Beware: Uneven surfaces and slippery steps in the tunnels. We’d rather you didn’t slip on the steps, stumble around in the dark or fall into the canal, so it’s essential to wear sensible footwear and bring a torch. NMW will make every effort to ensure safe passage for everyone on the walk but will not be held responsible for any injuries sustained.
This is the Underground Manchester tour, as featured in the Manchester Evening News, Daily Telegraph and on Granada Reports. And why? Because New Manchester Walks has unearthed the best stories about the mysterious world that lies under your feet, deep below the city: the subterranean rivers and canals, the abandoned tube line, the 1950s atomic bunker under Chinatown and the Second World War air-raid shelters.
On the Underground Manchester tour we drop down, down, deeper and down into the biggest of those shelters, built into the long-disused tunnel of the Manchester and Salford Junction Canal, where tens of thousands huddled in safety from the Nazi bombs inside its vast chasmic chambers under the most imposing and imperious brick work you’ll ever see.
We then head off along the tunnels to find the canal’s waters before they find us. Eventually we resurface to a lighter, brighter, finer-smelling world, and follow the route at street level, above where we’ve just been below, until none of us can get any further.
It’s a weird and wild world below and above. You’ll realise why after you’ve been down with us.
More details http://www.newmanchesterwalks.com/walks-tours/underground-other-unusual-things/underground-manchester/