A lot of good two soup cans and string did you when you were a kid. In the pre-SMS dark ages, sending secret, after-curfew messages to your buddy next door always got you grounded.

Still, you always had the neighborhood pool. But underwater communication? It remained strictly for the fishes.

If only you’d had Water Talkies. These genius devices, which were invented by a kid, make it easy to communicate underwater — far, far away from the prying ears of enemies (bullies, teachers, and, ahem, cool grown-ups). How’s it work? Just talk into the mouthpiece. No batteries, cans, or string involved. And it’s leakproof, so kids won’t drink the pool.

Voices carry up to fifteen feet, so this is probably not the optimal way to share a private Marco Polo hiding spot, but conversations remain secret from those on the surface.

Just remind the little buggers to take a break once in a while. Lest the conversation get too watered-down.

Available online at smarthome.com.