The group starts out on one side of the field or room with one person in the middle of the room.
The person in the middle will call out sharks (boys) or minnows (girls). He will then specify how he wants them to cross the room (running, backwards, hop on one foot etcÛ_).
It will then chase in the same manner that he called out. If one of the sharks or minnows are tagged they sit right where they were tagged and become seaweed.
This seaweed has to stay on their backsides, but they can tag other that are crossing as long as they are sitting. If tagged by seaweed the participants become seaweed as well.