Water play is always fun and it's the perfect thing to keep kids entertained, but near you while you are busy in the kitchen (if you're not including your little one in the process for whatever reason), here's a fun Halloween one we've made.
My daughter has always loved any and all water play and this Halloween themed one was no exception. I colored the water purple with food coloring, then I added in some plastic spooky things like skeletons, spiders, bats, snakes, and flies. You can find bags of things like this usually at Dollar Tree, Party City, places like that around Halloween time.
She wanted to use the pumpkin scoop with it so I let her of course, and we paired it with a purple bowl with spider webs on it to keep with the color scheme and the theme. Another bowl is almost always needed with water play since kids love to transfer so much. My daughter would scoop some water and things into the bowl, pour the bowl back into the bin, over and over for a little while.