H.sie's realism fix prevents you from diving for a certain amount of time when reloading externals.
Prior to the fix, not diving for a certain amount of time was a "personal" realism setting when reloading externals, along with good weather, and stopped. Sailor Steve had a good way to determine how long you had to stay on the surface and other penalties depending on how far into the loading process you were when you tried to dive. Can't remember the details off hand unfortuneately. I have them written down at home on my computer somewhere.
"Man them Flak guns boys!"