Oh the IXD2 is good fun, however I have found that I sometimes have to make a conscious decision NOT to dive when I have a plane inbound because it'll just slow me right down and it will hit me with a big fat stick of bombs before I'm safely submerged...
What I tend to do is turn away from the plane, crank the boat to full speed, and just keep running at 20 knots, then I tell my Flak to open fire only when the plane begins it's bombing run.
What this means is that the Flakvierling can expend all it's ammo on the plane coming straight at me instead of being busy reloading at that critical phase of the engagement, with a trained crew this usually takes out the plane before it drops its bombs. If not I make a hard 90 degree turn toward the Plane at the absolute last moment, causing the bombs to overshoot (usually
and not by much). If it (or my boat) is not going down by then, I crash dive, giving me enough time to get deep enough before it comes around for another pass.
Disclaimer:
this tactic is best employed against single planes, using it against multiple planes is dangerous and could be considered criminally irresponsible
also be careful if you are prone to nervous breakdowns, stress induced heart failure or weak of bladder
It also makes for some lovely screenies