Thank you so much for this! The idea with your little handheld net! In other videos I've seen is used a professional large kicknet, but your idea makes this study much easier, especially if this activity ig beeing done for a lot of kids at the same time!
That's not a riffle beetle at 6:36! It's not even a beetle. That creature belongs in the family Veliidae; probably in the genus Microvelia. Otherwise, a very good and enjoyable video.