Let's start with one global idea: a worm slide. The idea was for the children to place plastic worms (fishing lures without hooks) into pipes so when they poured water down the pipes the worms would be flushed down into another tub.
Here was the first version I built over 12 years ago. It was extremely simple. Two plastic PVC pipes were set on an incline using an upside down planter tray as a base.
Pictured below are some of the loose parts I started out with for this year's version of the worm slide. There was a white wooden tray, a narrow PVC pipe, a couple of crates and clear plastic tubing.
I started building the worm slide by placing a planter tray across the width of the small table. The tray was wider than the table, so it was important to make sure there was a drainage hole.
I taped the planter tray to the small table and then taped the pink crate on top of the planter tray.
I then set the white wooden tray across the width of the blue table. To tape it to the table, I crossed taped at each point where the tray rested on the lip of the table. One piece of tape went from the tray to inside the table and the other piece of tape went from the tray to the outside of the table and under the lip.