Yup, that was going to be the title of this post. I got the paper and was ready to write the post when I noticed that Peter scooped me and posted about the same paper today (yup, there is just not that many cool papers on Charismatic Marine Megavertebrates to spread around this week). I have nothing to add, so just go and see his post:
The results demonstrated that a free-ranging whale shark displays ultradian, diel and circa-lunar rhythmicity of diving behaviour. Whale sharks dive to over 979.5 m, making primarily diurnal deep dives and remaining in relatively shallow waters at night.