This is actually a meme originated from nico nico douga.
basically, in the scenery video that TV kanawaga used as a placeholder for the episode, there is well... a boat.
Sarcastically, someone puts a "nice boat" comment. (on nico nico, you can comment a video, and the comment will fly on the screen at the given time)
This thing quickly became a meme, and turned into something like this :
this is quite similar to the "nano" meme used, at each title screen of any nanoha episode.
this meme turned quickly into these parodies you could see here and there. (this might last for a good while, considering how it is on 2ch and 4chan)