The show centers on FBI special agents Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) who work on cases linked to the paranormal, called X-Files.

In Millikan, Georgia, biologists Paul Farraday and William Bailey discuss the decreasing frog population.

Agents Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) drive down to Georgia to investigate.

The agents talk to Dr. Farraday and visit a local bait and tackle shop that sells Big Blue merchandise.

Later that night, the bait and tackle shop owner walks through the swamp in boots, making fake dinosaur tracks.

Mulder wants the lake to be closed but the local sheriff declines and says that he does not have enough men to cover the 48 miles of shoreline.

The two find a large rock to climb up on and talk for a while about Mulder's quest to catch Big Blue, and the book Moby-Dick.

Mulder thinks the drop in the frog supply has caused Big Blue to move closer to shore and seek alternative food sources.

[1] "Quagmire" was written by Kim Newton, with substantial revisions courtesy of fellow writer Darin Morgan.

[3] "'Stoner' kid" (Tyler Labine) and "hesitant 'Chick'" (Nicole Parker) both first appeared in the episode "War of the Coprophages".

[5] The boat that Mulder and Scully ride on in this episode, the Patricia Rae, is named after the mother of director Kim Manners.

However, the rock set began to float and "an emergency crew of carpenters [...] worked furiously through the night" to reattach the platform.

[6] For the final scene of Big Blue, the producers had originally intended for a boat to pull a rubber sea serpent through the water, but they were unhappy with how it turned out.

It was just neat to have us separated from everything and stuck on this island where we could wax philosophical and kind of tell the truth to each other in strange ways.

"[12] Keegan also wrote positively of the conversation sequence, writing that the "isolation caused by the sinking of the boat [...] forces Mulder and Scully to actually discuss their issues.

"[12] Robert Shearman, in his book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated the episode four stars out of five, calling it a "delightful little gem" and "something rather magical".

Entertainment Weekly gave the episode a C and was critical of the entry's monster, writing "hey, the show kinda had to tackle Loch Ness".