The audio throughout the video/slideshow played alongside the photographs that the students had captured. Two different types of audio played, one of a woman speaking who was a professional sandcastle builder and another of children and a parent speaking. The diversity of the audio's create interest in the video and work well with what's going on in the photographs shown.
The sandcastles are temporary and the professional sandcastle builder thinks this is the best part, allowing the work to be destroyed and to let go of what took hours to create. The children and parent have a more relaxed attitude about it and also seem to think, by the audio, that destroying the sandcastle is the most exciting part.
Overall, the video was interesting to watch, and the diverse range of both the two different audio's showing one doing this as a profession, and others doing it for fun seems to work well.