If that video is real and showing some entity flying above the ocean surface and dipping in without any sign of impact with the water, it definitely seems like higher dimensional object is a possible explanation.

Imagine a 2D plane being an infinitely thin body of water with splotches of mud in some places. You as a 3D person can take a 3D pen and stab it into the 2D water, moving it around quite freely, but as you move it to muddy areas you'll get a lot resistance. So in order to move it laterally with more ease, you can just lift the pen over these muddy spots (vertically, the 3rd dimension in this case) and then back into the water on the other side.

From an entity confined to the 2D plane the will see this weird line moving through the water towards a mud spot and then slowly get smaller (as the pen pulls out and you see the tip finally) before it disappears and then reappears slowly on the other side of the mud spot. That's the 2D/3D analogy to what we could be seeing here in our 3D/4(?)D case.

I love thinking in higher dimensions, and this video looked like a good example of what it might look like. Higher dimensional objects would also explain some UFOs we see changing shapes mid air. (I'm actually not really a UFO follower nor avid believer, but check out the latest stuff from time to time)

Here's an example video about 4D hypercubes (tesserects)