Season 6: Episode 11 - The Mermaid Theory

The Mermaid Theory: After spending a lot of time with Zoey lately, Ted wonders if he should make more of an effort to get to know her husband "The Captain" so it is not awkward. Ted is very intimidated by The Captain, as Marshall points out that although he is always smiling but his eyes have a look of hatred. Ted agrees to go out on the boat with Zoey and the Captain for an evening sail. However, when he shows up it turns out Zoey is not feeling well so it is just the two guys. Once out at sea, Ted grown increasingly uncomfortable and becomes paranoid that the Captain is actually plotting to kill him. After Ted's fears cause him to go overboard, he bonds with the Captain and learns that he really wants to get to know Ted since he is a friend of Zoey. Meanwhile, Marshall is scared to spend time alone with Robin because of Barney's "Mermaid theory" which based on the history of sailors who after long periods of time out at sea would begin to imagine manatees as beautiful mermaids. Marshall fears that at some point he may grow attracted to Robin if he is alone with her too much. However, after their attempt to spend time together turns into lots of drinking- Robin throws up all over Marshall and he realizes she will never be attractive to him ever again. As the narrator tells these two stories, he tries to remember the fight that occurred between Lily and Barney in the midst of all this and has quite a difficult time remembering the details.