Building the World's First IKEA Boat

Summary
Mark and Ethan attempt to build a miniature boat using only IKEA furniture parts and cardboard boxes. Upon completion, Ethan names it "USS Engineer Boy Jr." After sending it afloat in their pool, the two later attempt to board the boat, but end up sinking due to their combined weight overwhelming the makeshift vessel. As it's falling apart, Fischbach and Nestor decide to go down with their craft as the video comes to a close.

Fake-out endings

 * After questioning Mark's methods, Ethan turns to the camera and exclaims "Just go for it, and if it doesn't work, quit", as the screen cuts to Unus Annus' outro timer for a few seconds before resuming.
 * After the boat sinks, Mark pretends to drown in his pool. The scene is then followed by dramatic piano music and a fadeout shot of Mark's memorial picture that reads "In loving memory, Mark "Unus" Fischbach", before cutting back to the video. The memorial wrongly attributes his alias to Ethan's Unus persona instead of Annus.

Trivia

 * Up to this point, Ethan thought that the Master of Business Administration (MBA) degree was actually called an NBA, in reference to the basketball league. After Mark had corrected him, Ethan called up his brother to confirm this statement, as his sibling was previously working towards an MBA.

Quotes
"Commit once and measure nonce (never)."

- Ethan Nestor-Darling on Mark's engineering methods