Winning votes:
[w] Sneak aboard the enemy vessel and search for the mage
[w] Set Goal: Defeat Mage
You figure the crew has been handling themselves alright so far, and those crewmen who were batted away before are getting up again and returning to the fight. Meanwhile, you don't know anything about what's happening below-decks other than them being a smaller group, so it's easier for them to be overwhelmed.
With that in mind, along with the fact no one has noticed the free plank yet and so it is a limited opportunity, you decide to sneak aboard and defeat the mage. In fact, defeating the mage becomes temporarily ingrained in your mind as you expend some magic, the mage is already defeated in your mind, the real world only needs to catch up.
Getting to the plank undetected was much easier than you expected, probably because everyone was focused on the main fight that was happening, That's a very good thing, because getting across is much more life-threatening than you expected. Going across a plank close to the ground is easy. Going across a plank between two points very high up in the air where both points are constantly shifting slightly? Not so much. In a...less than dignified but ultimately safe way, you crawl across to the other ship, gripping the plank for your life.
On your way across one of the pirates sees you and just sorta stops and stares. You blush at your less than heroic method of getting across being spotted. Then she gets grabbed by her shirt's neck and pulled onto the transport ship before she can get word to her allies about what you're doing. You swear you feel someone winking at you, it's a little unsettling.
After that happens you double your pace across and make it to the other end without further incident, you think you did at least. It looks like the pirates weren't expecting someone to sneak aboard, since they don't have any guards on the top deck, everyone is clamouring to join the fighting. On the other hand, the pirates are between you and the only door to below-decks. This was really a time you wished you had some kind of teleportation magic. Regardless, you sneak around behind the still large crowd of pirates, ever present of the rather large chance they have to simply turn around and spot you. You say some words of thanks to their love of battle as none of them do. Although...the crowd is rather big...maybe this wasn't the best choice...
Putting self-doubt out of your mind for now, you instead creep down the stairs, taking each step carefully to avoid making noise in the much, much quieter part of the ship. It's fairly well kept though, and nothing creaks, nothing you can hear over the still-loud yelling from above at least. Now below, you find yourself...not at a crossroads like you were expecting. From the layout of the transport vessel you were on you expected to have to choose between left and right, but on this ship the only path is to the left. So you head down that path, only encountering locked doors for some time. Just as you start wondering if this is the Corridor of Boredom all over again you catch the slightest rustling of fabric around a corner. Picking up your pace a little, you manage to get to where it was and find yourself at that crossroad you were expecting.
Down the side the fabric had been on you catch a man hurriedly walking around a corner, and you think you can hear several footsteps. Maybe it's where the mage is located, you're not really sure where else several people could be hurrying in this situation. Except maybe damage repairs? You're pretty sure someone like the Captain would have cannons on her ship after all, she definitely isn't the sort who'd go down without a fight, and she obviously has experience with this.
You turn your head to look the other way and jump back behind a wall in a hurry. That was the back of a pirate! You take a peek around; he's cleaning a rifle, back turned to you. You could probably get the jump on him. If you managed it right, you might even be able to get him to tell you where the mage is! Although, if you don't, he'd be able to raise the alarm on you...still, it's a quicker method than if you're wrong about following the others.
Hmm. Taking a risk trying to interrogate someone or potentially wasting time tailing a group... And there's still that niggling doubt telling you that maybe you should go back and help the crew fight off the pirates. But given the fact you're on the wrong side...
Either way, you need to make a decision
[] Tail the group
[] Get the jump on him (70% chance)
[] Go back and just fight off the pirates