Agua Mala

"It, it just doesn't live in water. It is water, taking shape only when it attacks, like it did when the hurricane backed seawater into the plumbing."

Written by David Amann
Directed by Rob Bowman

"If the sea is where life began - where our ancestors first walked ashore - then who's to say what new life may be developing in its uncharted depths."

— Fox Mulder

Mulder and Scully travel to Florida in the middle of a hurricane to investigate the deaths of a couple and their son. As the storm worsens, they end up trapped in an apartment with an injured police officer, an unstable man with an attachment to his gun, a pregnant woman and her boyfriend, a petty thief, and a Sea Monster hiding somewhere in the pipes.

Tropes:

Big Storm Episode: A hurricane is wreaking havoc on the shore in Floride during this episode.
The Bus Came Back: Arthur Dales, who formerly worked on the X-Files with Mulder's father, returns in this episode.
Cat Scare: "How the hell did that cat get in the washing machine?"
Doomed Hurt Guy: Greer. All that effort to save him and he dies because butterfingers Dougie, while stealing Greer's wedding ring, knocks a carton of Epsom salts into the tub with him.

Foreign Language Title: Spanish for "bad water".
Henpecked Husband: George. Although he and Angela aren't married, he otherwise fits the trope.
Karma Houdini: Dougie. Despite being a looter and inadvertently causing Greer's death (while taking his wedding ring no less!), the creep manages to escape in Greer's police SUV.
Improbable Aiming Skills: George manages to shoot a fire sprinkler while sitting down and holding his girlfriend turned around.
Instant Drama, Just Add Tracheotomy: Scully performs a tracheotomy on Greer after he's attacked by the monster.
Maternity Crisis
Monster of the Week: It's a Sea Monster eating people alive.
Only in Florida: "Don't all the nuts roll downhill to Florida?"
Sea Monster: The Monster of the Week.
Spicy Latina: Angela, George's pregnant girlfriend.
Too Dumb to Live: Though it doesn't kill him yet, Greer getting too close to one of the encased victims when the monster is clearly moving inside of it.