Definitely one for the bucket list, sphering is completely bonkers. Spend your stag do rolling down a 175m run in a giant bubble. It's mad genius and you're gonna love it.
You've got to just roll with it - literally. Half the fun of sphering is surrendering control and giving yourself over to the mercy of gravity. It's a bit like riding a rollercoaster, only far more intense.
Go for 'normal' sphering or upgrade to aqua sphering and make the run with 30 litres of water. It's not every day you get to find out what it's like to be inside a giant washing machine.