This might be a dumb question. But is the external hatch only Room #5? Or would you count the ones below as well?

icyewolf said:

The sub has three exterior hatches! I find the question relevant since sentences in the rules like: "A gnome may only leave the sub if the exterior hatch leading from the sub is first opened." (p. 10) seems to indicate that only one hatch exist. If you read on however, you will no longer have any doubts since the text reads: "Gnomes returning to the sub may enter through any external hatch, not just the one they used to leave." (Ibid.)