Only the bottom part of the ship is obscured by the mirror line, it never goes "over" the horizon it just keeps getting smaller in relation to the mirror line; the smaller it gets the more the bottom half gets obscured. Eventually the top half gets so small it passes the vanishing point.
It's all smoke (or ocean spray) and mirrors.
Yes it goes over the horizon since you are not able to ''zoom it back in full view''. You can clearly see the difference at 2:09 compared to at the start of the video, of course you wont admit this ever since you are schizophrenic.