What it shows:
Swinging a bucket in a vertical circle at sufficient angular velocity will ensure the watery contents remain within it.
How it works:
Provided that the angular velocity is such that the outward force on the bucket due to the water inside is greater than the gravitational attraction the bulk of the water feels when the bucket is upside down at the top of the circle, the lecturer will remain dry. The critical relation being
an arm length of 1 meter means a period of rotation of 0.5 seconds will suffice.
figure 1. swinging the bucket
Setting it up:
Any standard bucket with a handle will do. Don't fill the bucket too full. A transparent bucket would be ideal, but would spoil the idea in Comments.
A second identical bucket, filled with foam puffs or the like and hidden behind the lecture bench, will appeal to the clowns...