- Sink the USS Enterprise
- Sink the USS Denver
- Sink the USS DeHaven
This map is tough. Very tough. If a silver medal is enough for you, then all you have to do is dive to keep your periscope raised and watch for anything - plane or ship - to come close, then dive to depth level 4. Keep at depth level 4 until you're on top of the Enterprise, then get underneath it and fire torpedoes up at it to sink it. Sinking the Denver and the DeHaven, however, make the mission a lot harder.
Complicating this mission are not only destroyers, but also PT boats (which are immune to torpedoes) and every submariner's nemesis - the dreaded PBY Catalina. It's armed with sonar and depth charges, and is more than capable of ending your mission with extreme ease single-handedly. What was once the most worthless unit in the game is now the deadliest on the map.
Additionally expect the Catalina to have backup in the form of Dauntlesses and Avengers armed with depth charges. Unlike a destroyer's charges, these ones can hit you on the surface and cause unreal damage right off the bat. It is even possible for them to get lucky and drive a depth charge past depth level 2 and straight to depth level 3 - which sinks you in one hit if you're at that depth.
Fortunately for you, you have two submarines - the I-25 and I-26 - to aid you in this mission. They start in the northwest and southwest respectively. The Enterprise has already been identified for you on the map, so if you want to end the mission quickly you can.
At the start, get both submarines moving, and have them both make a beeline for the Enterprise. Raise the periscope of I-26 to spot and track a destroyer to the east of I-25, a Catalina, and several bombers headed out to I-26. Have I-26 crash-dive to crush depth to avoid these threats and head straight to the Enterprise.
- There's actually a simpler method - usually the first thing that comes into contact with the I-26 is the Catalina, so just surface and use your pea-shooter to shoot it down. However, for the Catalina patrolling around the I-25 it's a lot more difficult as there are PT-boats in the area, but it's worth taking some damage in return for the downing of this huge annoyance as this will turn the bombers of the Enterprise into headless chickens patrolling with no avail.
- The Gilmer will head for whichever sub is discovered first.
Using I-25, set a course for the USS Gilmer and perform the head-on attack to sink this threat quickly. With the Gilmer out of the way, you can try to surface and sink some of the enemy PT boats with your deck gun and machine gun (The PTs may attempt to torpedo you when surfaced - be careful!) but keep an eye out on the tactical map for destroyers, or worse - planes. Crash-dive as soon as you spot them.
Around this time, have I-26 look around for the USS Denver. If you can spot it, change course and engage the light cruiser. Ensure the cruiser's destruction with four torpedoes in her hull, but once you make the shot chances are the enemy will wise up to your presence and try to eyeball (yes, the computer can cheat and sink you with planes without using sonar) a depth charge hit - so make your first spread count.
Sinking the Enterprise
Once you've sunk the Denver, the only thing left should be the Enterprise and the DeHaven - which is a Fletcher-class destroyer and should be close to the Enterprise. I-25 should spot it shortly and perform the head-on attack to sink the DeHaven and complete the hidden objective.
Once the DeHaven is no more, you can try and surface to engage the last PT boats as you close in on the Enterprise. They may attempt to torpedo you, but so long as you don't surface too close to them, you should be able to avoid any torpedoes the Elcos send at you. The Elcos, unlike the Japanese Gyoraiteis, lack artillery pieces. This means you can use the deck gun and machine gun against them with impunity.
If you've surfaced to deal with the last PT boats, the only American unit left standing should be the Enterprise. If you're on the surface, the Enterprise may decide against launching depth charge planes against you. If it does not, take advantage of its generosity and torpedo the carrier to end the mission.