Finnatic:Mike I am not familiar with S drills or valve drills. Can you explain those?
S-drill = safety drill. Simply a practice run at sharing air. A modified s-drill is an abreviated version just going through the motions making sure that both regs are functioning and the reg you are going to donate is deployable.
A valve drill is going through valve shutdowns. A modified valve drill is just reaching back making sure you can reach them and that they are on.
Although I do know what a bubble check is, at what point do you do this? Before the dive or when you first submerge?
It depends on conditions. If conditions allow we'll do it at the surface. In rough OW conditions we may descend a little way and then stop to check eachother before continueing our descent.