I don't think this is either an exploit nor a bug. I put it here because this section is the de-facto standard for exploration movies.
Note: There are two versions of the movie.
The long one is for die-hard explorers who want to see it all exactly as it happened (94 MB, 5m43s).
The short version is compressed better, and has parts of it speeded up.
This is my first movie, and it shows my alt swimming to Gillijim's Isle.
It is uncut, and shows the FULL swim. So all you who just want to look at fancy exploration movies, skip this. Just check out the screenshot, or take the short version.
However, if you do some exploring youself, you might want to download it and have a look. I hope you can feel some of the excitement that I felt, when I did this.
When wall walking was nerfed, I figured the next frontier of exploration would be the seas, and not the mountains.
As we all know, wall walking was merely a small part of exploration, and mountains are still forced.
I did however, do some thinking about how to move freely in the seas. The result can be seen in the clip.
The music is Fatboy Slim - Right Here, Right Now
If you liked this movie, you might want to check out Total Freedom.