I felt the same about the underwater episode in Season 3. It's an incredible show!Rolling through series 5 of Bojack Horseman. Episode 6 " Free Churro" was......mind blowing. A landmark piece of television and it's a cartoon!
I've not watched 4 or 5 yet. Had been saving it, not wanting to blast through too fast.
Edit:
my thoughts at the time:
Bojack Horseman season 3.
Just watched ep4, Fish Out of Water. Oh my, just one of the best episodes of anything I've ever seen. BH is always pretty high quality , but this one just captures the series theme of loneliness and isolation beautifully. A real high point.