Goo Lagoon is a popular underwater beach located in Bikini Bottom. Since SpongeBob SquarePants takes place underwater, Goo Lagoon is made of a strange goo, hence the name, and the characters swim and surf in it. It first appears in the episode "Ripped Pants."
Goo Lagoon is broken up into sections, which include Mussel Beach, Goo Lagoon Sea Caves, the Snack Bar, and the Goo Lagoon Pier amusement park.
Weightlifting competition - Whoever lifts the most amount of weights wins. SpongeBob, Sandy, and Larry compete in this event in "Ripped Pants."
Surfing competition - Whoever has the best surfing moves wins.
Anchor toss competition - Whoever tosses an anchor the furthest wins. SpongeBob, Sandy, Larry, and Don competed in the 8th annual competition, and Sandy won.
Frank is a lifeguard. Larry the Lobster, a regular at the beach, also serves as a lifeguard. He can always be found here, either lifting weights, surfing, or lifeguarding. SpongeBob also once served as a lifeguard in "SpongeGuard on Duty."
Goo Lagoon Sea Caves (2) - A large cavern in Goo Lagoon. The only way to get here is over a rope bridge, from the sand castle. Inside, there are cave drawings, probably drawn by prehistoric Bikini Bottomites.
Weightlifting area - As seen in Lights, Camera, Pants!
Mussel Beach - A part of the beach where all of the bodybuilding fish hang out to lift weights, play volleyball, and frisbee.
Mount Climb-Up-And-Fall-Off - A mountain where one climbs up and falls off. It is located near Goo Lagoon Pier, as seen in the episode "Valentine's Day."
Goo Lagoon Pier - As seen in the Battle for Bikini Bottom and The Yellow Avenger video games.
Goo Lagoon is where most of the Bikini Bottom citizens spend their leisure time. Goo Lagoon is actually not a lagoon, but is a lake, as seen in many episodes of the series. Because they are already in the ocean, Goo Lagoon may be a dent or sudden depth in the ocean. Activities at Goo Lagoon include surfing, dancing, volleyball, weight-lifting, and tanning.
When compared to the Sand Mountain ski resort, Goo Lagoon is its summer counterpart. The weather is usually sunny at Goo Lagoon during the summer months, although it is not known what the weather is like during the winter months, during which many people flock to Sand Mountain. At some times, there is very windy weather.
There is a huge boat parking area out at the front of Goo Lagoon, and in Revenge of the Flying Dutchman, there is a bus stop. In the Employee of the Month game, the beach has a tanning salon which is run by a fish named Ray. There is a workout area for all of the beach buffs who hang out at the beach, called Muscle Beach.
Events and competitions that the beach holds include the anchor toss competition, a weightlifting competition, a surfing competition, and a sand castle competition.
A well-known lifeguard and beach buff is Larry the Lobster, one of the strongest creatures in Bikini Bottom. He commonly impresses many women well. He is one of the many lifeguards and beach buffs who works and spends time at Goo Lagoon.
Sheldon J. Plankton of the Chum Bucket planned to open his second restaurant called the Chum Bucket Mega Bucket on Goo Lagoon. He hired SpongeBob to help demolish the beach's property with assertiveness. However, after discovering Plankton's motives, he regrets his actions and revives Goo Lagoon for everyone, so the new restaurant Plankton planned was never built.
The Flying Dutchman has buried treasure on the beach, as seen in Revenge of the Flying Dutchman.
In real life, there are such things as underwater lakes and lagoons, as seen in this video and explained in this Wikipedia article.
Seasons 5 and 10 are the only ones in which Goo Lagoon doesn't appear.