The biggest ships and the largest cannons in the world are useless if there is no way to detect their targets. Here are the sensors that you will be facing in Silent Hunter III.
- Silent Hunter III Manual

Eyeball Edit

Up to this day, the human eye has not been completely replaced as a detection tool, and its importance is never diminished at close range. Periscopes, torpedo wakes, and partially submerged conning towers can be spotted easily by an alert watch.

Keeping completely submerged will obviously help you avoid being seen, but there are times when you need to take a peek outside or run the boat on diesels. For those instances, try to keep your profile (be it conning towers or periscope) as low above the surface as possible. Use darkness to your advantage, and never keep the scope up more than it is needed.

- Silent Hunter III Manual


The primary ASW sensor used throughout the war by Allied escorts, ASDIC (named for the Anti-Submarine Detection Investigation Committee) relies on sending sound impulses through the water and listening for echoes from submerged objects. Early models projected an almost horizontal beam in the forward hemisphere of the escort, and were unable to tilt it in the vertical plane. The consequences were twofold: the depth of the target could only be guessed, and contact was lost when the escort approached the target.

To defeat ASDIC, try to present the minimum possible silhouette to the escorts. This may create a weak echo that will be ignored or lost on the way back to the sensor.

Another way to avoid detection would be to "use the vertical." Move on the surface - the waves create distortions that prohibit the proper travel of ASDIC waves.

- Silent Hunter III Manual

Hydrophone Edit

A primary detection tool on submarines, the hydrophone was only of secondary importance for the escorts. Still, even if not providing input sufficient for an attack, it could detect a U-boat and prompt a search by ASDIC.

Detection by hydrophone is best avoided by keeping noisy activity at a minimum in the U-boat by giving the Rig for Silent Running order and running your engines on Slow Speed - the setting that creates the least cavitation and noise.

- Silent Hunter III Manual

Radar Edit

Used by both aircraft and escorts, radar can detect a target miles away, much beyond your visual range. It relies on the same principles as ASDIC, but used radio waves instead of sound. Advantages in technology led to even the snorkel head being detectable towards the end of the war.

Avoiding radar is difficult. As with ASDIC, the strength of the echo depends on the profile presented to the sensor. Useless you're skimming the outer limits of its range, however, it wouldn't make that much difference. A much better defense would be submerging and not presenting any profile at all.

- Silent Hunter III Manual