I named this exercise in response to the idea our tides are slowly rising, like you will as you perform this plank variation.
Start in a regular elbow plank position. Raise up to your hands and walk your hands and legs to the right one length. Lower onto your elbows. Lift back up and walk your hands and legs to the left and lower onto your elbows. Each time you lower onto your elbows counts as one repetition.
You can walk further than one length each way, but this method is for more stationary settings.