Lumberjanes Vol. 6: Sink or Swim has a theme of oceans and sailing. April is working on the badges for the nautical life skills section of the camp handbook and wants to prove to the new counselor Seafarin' Karen that her cabin is a good team after finding out that everyone in the cabin has to be a good team and all tie good knots to earn the "All For Knot" badge. After only thinking of herself and her love of mermaids in the previous volume, she doesn't want to let down her friends again. The girls end up finding out that Seafarin' Karen's ship has been stolen by selkies that keep taunting her and keeping the ship within view but protected by whirlpools and that Seafarin' Karen is a werewolf. Weird things don't surprise the girls so much anymore and they decide to help Seafarin' Karen and also show her how great a team they are. The group actually splits up with Molly and Ripley going to see if the bear woman knows anything about selkies and April, Jo, and Mal trying to help Seafarin' Karen figure out a plan to get her ship back.
Molly wishes that she was something more interesting like all of the people that she has met who are involved in the supernatural and that she didn't have to leave it all to go back home when the Summer ends. She is given the choice of sticking with the bear woman to learn more about the supernatural but she chooses to go help her friends and the bear woman says to herself that she's not ready yet. Maybe the story will return to this in the future when Molly is more ready since she seems to have more potential in the area of the supernatural than the others, especially in the end when the spyglass, which is used for spotting supernatural things, shows that all of the girls are glowing after being involved with the supernatural but Molly is glowing more than the others. Earlier in this volume, Molly mentioned how she remembers the bear woman saying something about the woods and how it changes people and wants them to stay so maybe the woods have chosen Molly. We have already seen hints of how she loves being at camp and dreads going back home because there isn't an exciting life waiting for her back there. Camp has also helped her figure out who she really is. It means a lot to her so maybe this supernatural life is where she is meant to be.
As with every volume, there is an emphasis on friendship, getting along with each other, and working together. This is always evident with the girls of the Roanoke cabin but in this volume it is also evident with Seafarin' Karen and the selkies since they are enemies that turn into friends. The selkies stole Seafarin' Karen's ship because they thought that she stole one of the selkies' pelts but in reality the pelt was stuck in a magical portal in the water. The ultimate reason why it was there in the first place was because Seafarin' Karen had it in her mouth and was tossing it around while in wolf form and it ended up in the water. Due to all of them helping each other while caught in a stormy sea of magical portals, they forgave each other for all of their anger and hurt towards each other and decided to sail away together. And the girls of the Roanoke cabin earned their "All For Knot" badge. Such a happy ending!