The Lagoon is a small bay on the island connected to the ocean by a waterway which seemed to bend to the shore out of side from in-land. It had a waterfall being emptied into it, and the Castaways sometimes swam in it which could be an indication that it is freshwater. Since the Lagoon's water is often calm, most of the island visitors are seen arriving or leaving by means of the Lagoon.
The Lagoon was also the site of the sunken ship of Fifi LeFrance and her husband Ricardo Laughingwell, who formed the South Sea Film Productions. After they were married, they sailed on their yacht to the island on their honeymoon to make a motion picture together. Their yacht somehow sunk, leaving their film, camera, and costumes for the castaways to find years later. It is unknown if they were rescued or died on the island.
The Lagoon was also a catch-all for all sorts of objects being washed up near the island including a government attaché case, a crate of coconuts, a box of radioactive seeds, a live lion, tubs of ice cream, an experimental jet pack and a crate of magician's tricks possibly linked to Laughingwell's yacht. A pirate's chest, the Eye of the Idol and tiki-statue of Kona were found buried on separate occasions within the same proximity of the lagoon. The Castaways subsequently built a Lookout Tower to the side of the lagoon to watch for ships on the shore.
The lagoon was also a source of food for the castaways on the island, for they caught fish, as well as lobsters in the lagoon. It is also the scene where several objects wash in from the sea such as a military attaché case, a crate of radioactive vegetables, a box of plastic explosives and other objects. Visitors also tend to land here, such as Boris Balinkoff, Jackson Farrell, Duke Williams, Erika Tiffany Smith and a Japanese Sailor among others. The Professor once placed a stick in the lagoon with markers to keep track of the water level on the isle. Gilligan once put his lobster traps on that stick, and was placing it in deeper water to catch larger lobsters, which led the Professor and the others to believe the island was sinking. The Castaways have also dug up items here like a tiki statue, pirate chest and a rare gem that seemed to grant three wishes. The digging of a lobster trap, however, seemed to cause a section of the bank to float out into the lagoon.
- The Lagoon was constructed on a CBS back lot. It was located about half a mile from an interstate roadway and the sounds of rush-hour traffic often resulted in huge delays in filming.
- The Lagoon was about 4-feet at its deepest point.
- Filming of "Gilligan's Island" occurred during the fall and winter months and required cast members to sometimes swim in the chilly 50 degree water. Bob Denver often wore a wet suit under his clothes to combat the cold temperature.
- During the summer months, the Lagoon would become stagnant. Bob Denver and Alan Hale once put a live fish in the water which died. Network executives were hesitant to change the water until the cast demanded the executives swim in the same water they had to.
- The ending of the second and third seasons show the Castaways still waiting to rescue beside the lagoon, although this might not be the same location as it appears much larger than the small bay seen in the series. A "Mad TV" episode shows seven skeletons still beside the lagoon... still awaiting rescue which is completely contradictory with the later movies.
- Castaways Pictures Presents
- Feed the Kitty
- The Invasion
- It's a Bird, It's a Plane
- It's Magic
- Not Guilty
- Quick Before It Sinks
- Three to Get Ready