In book seven of the Chronicles of Caleath, ADRIFT: In Search of Memory
the adventures take place on a tall ship. There is a scene where Caleath spends some time underwater... well there are a few moments... but I am not giving anything way here... Only to say that seeing these sharks, and how they move through the water without being threatening, inspires me to write!
The sharks in the Chronicles aren't grey nurse sharks...I will say no more. :)