Some people said:
”A: If they're in soil, and it rains, within 2-4 days. I brought these to college, so I played a bunch of pranks with them... I never really kept track of where they went. But I did launch one fairly close to my dorm, and I didn't see it the next day on the ground... So maybe 2-4 days are an exaggeration. They're worth it tho. Have fun”
People say they use them in lakes, etc.