Great suggestions Rafiki.
I setup my gopro for time lapse for our passage through the panama canal. I set it up at about 6 am before we started our passage, and it ran it'll about 4 pm as we exited on the Atlantic side.
I used a portable battery pack I bought on
Amazon. It was a 18000mah Anker portable charger, and it has 2 usb ports for charging phones and tablets. I also bought a skeleton case for my gopro4 so I could access the usb port on the side of the camera. Since the skeleton case isn't weather proof, I used a zip lock bag over the camera, cut a small hole so the lens would not be covered by the bag, and ran the gorilla pod and usb cord out the bottom of the bag. I used so string I had in my suitcase to secure the bag to the camera and gorilla pod, and attached the gorilla pod to the railing.
With the battery pack attached, the gopro ran from 6 am to 4 pm and still had more than 50% charge left.
Sadly I didn't like the results... I was on deck 6, and aimed the camera out at about a 45 to 60 degree angle out... the rocking of the ship is very visible from this view, and seemed too distracting and I don't have the appropriate software to stabilize it. I used some free software but it killed the image quality....