Why does the crash dive go to ~70m?

[sharkbit]

It is embarrasing to crash dive into the bottom though.

Not that I've ever done that though. I've just heard of it happening.

No really...I never have.

As has also been stated, DO NOT interrupt crash dive until it has finished i.e. levelled out at the pre-set depth (default 70m). Doing so can have some screwy effects.

I've never had a problem CDing from the surface and hitting the A button at the depth I want to level out at. My sub overshoots the depth but comes back up and levels off without any problems.
I haven't tried setting a different depth on the depth gauge during a CD though. That may be an issue.

I have had depth control problems when CDing from periscope depth. My sub just keeps going down and depth control is very difficult. You have to maintain a higher speed to stay level which causes problems when trying to evade the destroyer that caused you to CD in the first place.