how do you measure dive times correctly?

like the title says, how do you measure dive times?


first what qualifies as a dive and how should it be measured? should you measure the dive at flank or full stop? some other speed?

is it only counted after you level off at periscope depth?

is it counted as soon as the tower is covered but scope is still showing?

is it measured by crash dive or regular dive?


i dont even know what the dive time is supposed to be but i first need to understand HOW its measured so i know if im doing it correctly.


the reason i need to know all this is i want to test the s-class to see if they have realistic dive times and if not i will try to set them correctly.