BUM WALK
This may look a silly exercise, however it does work.

Have your legs out in front of you, sitting upright.

Lift one side of your buttock, and pull yourself forward, with the aid of your heals, repeat on the other side to lift and pull yourself forward.

You can use your arms in a canoeing action to get a good rhythm.

Go forward then come back, ideally on a smooth surface or carpet.

Suitable for most fitness levels. Aim to increase your distance traveled both forward and back each time you do the exercise.