The Jellyspotters are an expert Jellyfishing fraternity. Most of them are anchovies who often speak in unison with their trademark "meep," with real dialogue thrown in.
Many fans admire them and take every bit of advice that their leader, Kevin the Sea Cucumber, shares with them. One of their biggest fans is SpongeBob. In the episode "I'm Your Biggest Fanatic," they are revealed to be less than what everyone thinks they are. Kevin, taking advantage of SpongeBob's obsessive need to join the club, takes him out to Jellyfish Fields to haze him. These gags prove less than successful as SpongeBob excels at every "test" and even calms a King Jellyfish after Kevin inadvertently antagonizes one.
Kevin and the Jellyspotters show their true incompetence in this incident, with SpongeBob easily saving them from painful electrocution, and was admitted into the club after winning the admiration of Kevin's gang. Kevin was replaced with SpongeBob, who quit though, realizing jellyfishing was all about the sport, not about Kevin. The club's only known members were five anchovies and Kevin. According to the latter, many tried to join the club, but were rejected.
The group is comprised of mostly, and now, possibly, just anchovies.
The only known former member is Kevin C. Cucumber. He was the leader until SpongeBob saved the Jellyspotters and they kicked him out.
The only known potential member is SpongeBob SquarePants. He was offered the position of the leader, but he turned them down.