The Reef Blower website exists to fit multiple things like SpongeBob episodes, Shrek Movie, Bee Movie, etc... In just a ridiculously small gif or video and that all to just fit in the 1 GigaBytes of the storage in Neocities.org!
The MP4's (mostly) have audio but the GIF's have an audio file given with the media since GIF's cant have audio. The audio files bundled are not very likely to be compressed and just being "understandible" or "tolerable".