On a second and third look, I maybe incline to good boat handling. If you compare the video to the photo
of the harbor, you can pick out the breakwater with the light tower on it.
Notice that the boat comes past the seaward
end of the breakwater and cuts sharply into its lee. Then water
over the breakwater picks it up and slides it sideways just enough so that the combination of motions shoots the boat through the gap.
If they don't cut in hard, I don't think they make it. And it doesn't look as though there's enough room to go around and try again.
So, good boat handling, reading the water
and judging speeds.
Or, alternatively, a lot of luck.