During Noonan's ambush of Vane, his henchman's pistol misfires. This was a common problem with flintlock weapons, either due to the flint becoming dull and failing to produce a spark, or damp powder.
When Richard Guthrie tell Miranda Barlow that he must "absorb the blow, as it were, like a rocky promontory" this paraphrases a famous passage from Marcus Aurelius' "Meditations" which she had lent to him in an earlier episode.
During the first scene on the beach during the careening, one member of the Walrus crew appears to be playing the "Parson's Farewell" on a mandolin. This piece is a recurring theme in the music of the show.
When Eleanor looks out from her balcony to the harbor after being told that the Andromache has arrived, there appears to be a flag flying over a tent that is very similar to that of real life pirate William Moody, albeit with a different color scheme. The flag is red with a heart with an arrow going through it, both black. Moody's flag had a black field, the heart was red and the arrow was white.
There are 2 character deaths and 3 unnamed character deaths (2 in the flashback) in this episode making the season count 52.