I never have this problem. Are you doing these things?....
- Travel at periscope depth in the daytime when in enemy waters
- Only travel on surface in poor visibility situations such as night and storms.
- Don't leave your periscope up. Raise it up, look, and take it back down.
- Try to put the sun behind you when approaching the enemy
- Use 1/3 speed for regular movement so that you are hard to detect by hydrophones. I only use higher speeds for chasing down convoys
- Drop below 55ft every so often and do a 360 degree sonar check of your surroundings
- Dont approach a convoy directly. Get ahead of its travel path and setup an ambush at 90 degrees submerged with engines off. Dont go to the enemy, make the enemy come to you.