This is a time-lapse video shot using Instagram’s Hyperlapse app on an iPhone 5s. The camera is mounted rigidly to the boat but the software is able to stabilize the video utilizing the accelerometers in the phone. This is why the horizon is stable but it looks like the boat is moving in relation to the camera.
App: https://hyperlapse.instagram.com/
Suction cup mount (Amazon Affiliate)
US: https://amzn.to/2TjZ77Q
Camera holder: https://amzn.to/1O4KwUX