As othe people mentioned, it is very reasonable to order a crash dive as soon as the plane is spotted. In some areas it is recommendable to even have a finger ready on the C button while surfaced.
On the last patrol in the Indian ocean I decided not to take it any more. I wanted to fight back. Two catalinas I think. I manned one flak. The AI guy on the second flak did shoot but did not hit anything. And I thoght I must have landed few hits but no effect to be seen on the planes. In this battle I lost four crew members, all while servng the flak. And no success against the planes. I will not be fighting them any more I think
