My mother found this washed up on the beach after recent storms.

It's a orange hard plastic package case. Size is about the same as a package of old bay seasoning. I'd guess it's supposed to have a cap to make it water proof.

Inside was a ripped up package. It's some kind of plastic/metal foil and it has been ripped (seagulls maybe). It's pulled out slightly for the picture.

The substance feels like clay, made the fingers smell AWFUL and the stench didn't get fully washed off yet.

What is it? Looks like C4 in games/movies but can't find pictures matching this look, and want to know if we need to call the police about the find.