Your goal is to avoid detection, else be destroyed, you need to constantly work to maintain your stealth and invisibility, while making sure that you can spot merchants and warships effectively and efficiently. You have to stay undetected before, during and after your attack.
- As in hunting elk or deer, during the hunting season, the first to spot the other usually wins. If the enemy detects you or sees you first, you’ve just lost nearly all chance of winning. If you see them first, and dive or get yourself into an advantageous position, you’ll usually win.
- Your best chance of detecting ships, thus being able to act accordingly, is when you’re surfaced and you have a watch on the bridge of the conning tower, keeping an eye on the ocean and horizons. The hydrophone is an auxiliary device, effective only underwater. It’s useless when the submarine is surfaced. It visibility, safety and the element of surprise allow, you should be surfaced, else you’ll maneuver around blindly, and not only leave yourself open to surprise by Allied ships, but also lose valuable attack opportunities.
- When a ship is spotted, dive when you see the mast or top of the funnel(s) of their exhaust stacks. Though not always reliable, ships have lookouts in the masts. Warships sometimes have optics in the foremast (front mast on a ship) that can spot you from a distance. It’s better to submerge too early than too late.
- If the region you’re in in heavily patrolled by aircraft or warships, stay submerged from dawn to dusk. You can keep the charge on your batteries going long enough to get to dark by moving at Ahead Slow (1 on the speed UI) or slower. Then, surface after dark to recharge your batteries and maintain a watch on the bridge, submerging again when dawn comes.
- If you’re stationary, you’re submerged.
- If weather conditions limit visibility and prevent effective watch on the bridge, such as heavy fog on the seas, submerge and use your hydrophone. With limited visibility, there’s a chance a ship could suddenly appear, or aircraft suddenly appearing to spot you. With the limited visibility, the hydrophone is going to be the most effective way to detect enemy ships, anyway.
- Do not stay in the same location where you’ve dived. Not only could the enemy possibly have your position at the time of the dive, but sometimes oil can be left behind from the tanks and equipment, because of a residue that lingers in the compressed air tanks used to fill and blow the tanks for diving and surfacing. After you’re submerged, leave the location of the dive. Without a mod, the second point is mostly an immersion and historical accuracy point, but in either case I’ll still move away from where I dived.
Avoiding Detection – The Periscope
No matter the case, your periscope is always low when you’re using it. Even when the ships are out to 5 or 6 kilometers. As was mentioned earlier, a periscope is an obvious indication of a submarine, a recognizable silhouette.
- Do not use the periscope during the day when you’re surfaced. It creates a higher silhouette and the typical, recognizable shape of a submarine.
- When you get closer to the enemy 1-2 kilometers or shorter, keep your periscope low enough to be awash in the waves. Sure, it the water laps up onto the periscope lens, momentarily blurring your view, but it’s the best way to hide it when you’re close.
- At short ranges, don’t leave your periscope up. Only use it for a little while, as long as it takes to do what you need to do, then bringing it back down again.
- Travel at a slow speed when you have your periscope up. Not only do higher speeds cause vibration in the periscope to make useless, but the periscope cuts a draft in the water when at higher speeds, spraying water out behind it and giving away your position.
Avoiding Detection – Surfacing
Always be careful when you surface. Don’t just come flying out of the drink. This is especially true when you’ve been underwater for an extended period or at a deep depth. For all you know, there’s something up there waiting for you, or something you hadn’t detected. Going up carefully will also maintain your stealth if anything is detected visually or with your hydrophone. If at any point you detect something, feel free to hunt it or stay hidden. It’s your choice, but the point here is not to sacrifice your stealth when surfacing.
- First, go up to about 20 meters and do a 360 degree sound check with the hydrophone, moving at a slow speed. If there is something up there, 20 meters will keep you below their keel and safe from being rammed.
- If there’s nothing up there, get up to periscope depth quickly, but not above 9 meters (depending on weather conditions). Do two 360 visual checks with the periscope, one without magnification, one with, being careful to pick up any relevant details that may catch your eye.
- If all is still clear, get up to a high speed before you surface. Not only will this get you onto the surface quickly, but it will also allow you to dive just as quickly if you need to. Get out there as soon possible and personally do a 360 degree check with your bincoulars. If you’re nervous about it, do it again with the UZO on the bridge. In the case of U-Boats, this is going to be especially important in the latter stages of the war, where Allied equipment and instruments have been improved and their anti-submarine tactics nailed down.
Avoiding Detection – Aircraft
Submarines are very vulnerable to aircraft, so consider every spotted aircraft as hostile unless proven otherwise. Even in friendly seas, in which an errant enemy aircraft could be lurking. Submerge temporarily or dive to a deep depth. Either way, do it quickly, and keep in mind that the aircraft has a bird’s eye view and may spot you if you aren’t deep enough, which means that you need to spot them early with the watch on the bridge. Your best bet, upon spotting aircraft, is going to be diving as deep as you can as quickly as you can when aircraft are spotted.
- Aircraft can’t spot you as easily in rough seas. However, if your submarine is silhouetted against the horizon, it will spot you as easily as on calm seas.
- Aircraft have a hard time spotting you in in poor visibility conditions or bad weather.
- It is especially true in both of the above when your submarine is travelling at high speeds, because the submarine’s wake when travelling on the surface is more noticeable than at other speeds.
- Your best chance for attack opportunities will be by observing the seas around the submarine when surfaced. It is less risky to do in clear weather, because aircraft can be spotted from a greater distance. They can be spotted in time to safely dive, thus you can still be surfaced for spotting targets. It doesn’t mean the risk is gone, however, and this doesn’t include areas where the seas are patrolled by warships, which will have surface radar.
- In areas patrolled by aircraft, as was mentioned, don’t surface when there are low clouds or fog. Aircraft could suddenly appear, and you won’t have the time to dive to avoid being detected or attacked by the plane.
- A darker color scheme painted onto the horizontal surfaces of your submarine makes it harder for aircraft to spot you when submerged. This is more of an immersion and historical accuracy point, though a mod would make this accurate in-game.
- When the sun is bright and cascading into the water in calm seas, it can make it easy to spot you, even when you have a dark color on the horizontal surfaces. Everything can be seen more easily because of the contrast in light.
- Without the bright sunlight, dark water is a mass that hides everything, even something as big as your submarine.
- Rougher seas, even in bright sunlight, is a constantly churning body of water. When in sunlight it creates a constant refraction of water across the surface of the waves, making it almost impossible to see beneath the surface.
- The speed of an aircraft makes it very difficult to spot a submerged submarine until it’s almost directly above it.
- The Mediterranean and Baltic usually have the most turbulent seas, and along coastlines where weather is more erratic. Mouths of rivers and outlets are usually rougher, too. In open seas, however, though rough seas can be common, you usually have calmer seas, and aircraft will have a better chance of spotting you.
- Regardless of your speed, a submarine’s wake can be spotted by aircraft, given the seas are calm.
- Aircraft can spot a periscope, but it’s very difficult. Avoid using your periscope to monitor the skies after diving to hide from aircraft. If you’re submerged and an aircraft arrives, lower the periscope until it has passed.