Recap / Eureka In Too Deep

A romantic meal in mobile lab at the bottom of a lake? Yep, sounds fine.

Jo: I have a thousand reconstituted lungfish in the Estivation Lab, the Thermodynamics Wing is now a sauna... Oh, and the cafeteria floor is a trampoline.
Zane: You're kind of missing the point of Feynman Day, aren't you?
Jo: Oh, you mean there's a point to all of this idiocy?
Zane: Yes. Some of the greatest innovations in history were the result of a really cool prank. I mean, how do you think we discovered anti-matter? And Velcro.
Jo: Seriously?
Zane: Well, no, but it's possible and you're kind of squelching that potential.

It's hard to tell pranks from real emergencies as Feynman Day sees Carter and Allison trapped in an underwater lab.

Tropes

• Altar the Speed: Carter and Allison hadn't agreed to a wedding date yet but decide to get married right away as they're in danger of drowning.
• April Fools' Day: Feynman Day is Eureka's equivalent, with high-tech pranks all over the place. A helicopter is shown upside-down on the GD roof, Larry is speaking like a dolphin and Jo's outfits keep turning into catsuits.
• Beard of Sorrow: Fargo has been taking sick leave to spend all his time with Holly, and appears to have done very little grooming since then. Turns out this is because SARAH can't support Holly long term, so he wants to spend time wit her while he can.
  Allison: Fargo, when was the last time that you slept or bathed or weren't here?
  Fargo: My love can neither sleep, nor bathe, nor leave, so I shall do none of these until she can. Oh, and don't worry. I have plenty of sick days accrued.
• Call-Back:
  • Dr. Fowler's teleporter returns, as issues with the targeting system cause most of the problems in the episode.
  • When Zane isn't sure he's up to being Head of Section Five due to his immature reputation, Fargo tells him that his reputation was no different when a time shift put him in charge of GD.
  • Allison is still holding onto some insecurities about Carter's matrix relationship with Jo.
• Chekhov's Gun: Virtual Vincent, Carter and Allison's maitre'd on their underwater date. He continues working after the accident, giving them a way to communicate with GD.
• Dissonant Serenity: Virtual Vincent's tour has some less-than-helpful things to say as Carter and Allison's predicament wanders away from the tour parameters.
  Virtual Vincent: At this moment, you'll get a remarkable view of the famous Archimedes Trench; but you wouldn't want to take a plunge into that abyss, that thing... is crazy deep!
• Distinction Without a Difference: After shooting down Carter's idea of using torpedoes, Allison realises they can use the sub's deep-sea probes to push themselves back from the brink of the Archimedes Trench. Pointing out that this sounds very similar to torpedoes earns Carter a Death Glare.
• Failsafe Failure: The marine lab's airlock fails to keep the water out.
  Carter: What's the point of an airlock that's not airtight!?
• Gleeful and Grumpy Pairing: Jo thinks Feynman Day is stupid and dangerous, while Zane thinks it's a hoot. Pranking her so her business suits turn into catsuits doesn't help. She turns it around on him when he's about to take over Section Five, turning his usual T-shirt-and jeans ensemble into a suit.
• Godzilla Threshold: Carter and Allison being rescued from their leaking submarine with a patchy-at-best teleporter that's caused no end of problems just that day certainly counts. Notably, when Carter expresses concerns about potentially being spliced with random fish into some kind of mutant merman-type thing, no one gently corrects him as they usually would, suggesting it's actually possible. However, with ten minutes of air left and no rescue available for hours, there's little choice.
• Grand Romantic Gesture: After hearing Allison's plan to wait out Feynman Day in the marine lab, Carter sets up a romantic lunch together, hoping to get the ball rolling on wedding plans. Instead, all their tensions and issues come to the surface, and when they try to turn back, a mysterious underwater vortex damages the lab, sending them to the bottom of the lake.
• Green-Eyed Monster: One of the fights between Carter and Allison stems from Allison spotting Carter talking to Jo in a catsuit earlier that day. Carter retorts that Jo was helping him set up Allison's surprise, and the catsuit was Zane's fault.
• Innocent Innuendo: Holly, naturally, when Fargo and Andy both exit the same small room.
  Allison: Is anyone else going to come out of there?
  Fargo: It's a closet, not a clown car.
  Allison: Okay, what were you guys doing in there?
  Holly: They were both servicing me.
  Allison: I'm sorry that I asked.
• Ironic Echo: Discussing their relationship issues, Carter is dismissed when he expresses the fear that Allison is dragging her feet because of his intellectual shortcomings. Later, he repeats her words when she expresses insecurities over his matrix relationship with Jo.
  Allison: This is your issue, not mine. What do you think? I go around comparing your IQ with my previous husbands?
  Carter: I do now! [Later] You think I spend my time with you thinking about Jo in a catsuit? That's your issue, not mine!
• Locked in a Room: Carter and Allison are trapped in a submarine together, that has sunk below its tolerances and sprung leaks. They end up discussing their relationship issues, such as Carter's insecurites (that Allison is dragging her feet over picking a wedding date, hasn't told her family she's marrying him, and he's worried it's because he's not as smart as Allison) and Allison's anxieties (their lives keep getting crazier, getting married means Carter will be her kids' parents and what if they don't work out?).
• Skip to the End: Carter and Allison get married while in a lab that's filling with water, so Carter asks Henry to speed up to the important parts.
• Shout-Out: When Carter suggests firing torpedoes, Allison is less than encouraging.
  Allison: This is a marine lab, not the Red October.
• Unwitting Instigator of Doom: Dr. Fowler's teleporter's faulty targeting system causes the episode's problems by damaging the marine lab when Carter and Allison are out in it. He ends up fired.