[Dread Knot]

The way I see it there are five factors in real life missing from the game that kept WW2 skippers from just nosing into a harbor when they got bored.

Lack of good maps. The ones in the game are perfect. You even have an optimal overhead GPS view of where you are all the time. In the actual war, there often were no good maps at all. When Mush Morton made his famous recon of Wewak, he had to rely on a crude blow-up from children's atlas that one of his crew had providentially brought aboard. A serious difficulty for both sides with naval operations in the Pacific was the lack of good hydrographic charts. In some cases, the only available charts were British Admiralty charts dating from the 19th century. These were reproduced and issued by the US Navy, but often with disastrous results as they were inaccurate and out of date.

Shallow Water. In SH4, the bottom is always flat, fairly constant and in reality, featureless like a swimming pool. All those rocks you see are simply graphics there for show. You can pass right through them. It's almost impossible to run aground unless you ram the beach. In the real world, the bottom of any harbor can be a minefield of unknown obstructions. Logs, coral heads, wrecks, reefs, rocks, planted obstacles, dredging spoils, sand bars, etc. Anyone of which could damage or hole a submarine. Shallow water always tends to be more subject to treacherous tides, eddies and currents probably all of unknown strength (due to poor charts) which would be difficult for the electric motors of a submerged submarine to overcome. There are none of these in SH4. In addition a submarine is far more visible against the bottom in shallow water by aircraft.

Harbors are busy. In SH4 most harbors (even the big ones) are rather thinly populated and lifeless. In the real world major ports are a crowded hive of constant activity. There are lighters, barges, auxiliaries, coasters, yard oilers, motor boats, tenders, coastal minesweepers, ferries, tugs constantly on the move, even at night. Most happily dedicated to putting out the alert if they spot periscopes or any strange activity. The game doesn't even begin the simulate the diverse number of small craft that took part in the war in the Pacific. Most Japanese mainland ports also had a dedicated contingent of shore patrols and searchlight posts manned by men who did nothing but scan the waters day and night.

Nets. Most large harbors had them, not only at the port entrance, but often deployed around important vessels as protection against torpedoes and frogmen as well. These harbor nets had dedicated tenders who would be another obstacle to dodge. In addition, most warships had a constant patrol conducted by armed members of the crew who would man a boat and row about the anti-torpedo net in shifts to maintain them.

The Unknown. In SH4 by living multiples lives and careers you learn the AI's predictable habits and which harbors are weak. In the real event, no one had anyway of knowing what sort of nasty surprise was waiting in any particular port. The US and Allied navies often assumed that Japanese harbor defence procedures were the same as their own (after Pearl Harbor quite stringent) and acted accordingly. A US skipper thinking of penetrating an enemy anchorage had only to dwell upon the well-publicized Japanese midget submarine operations into harbors which invariably ended in either suicide or captivity with little gain. That sobering fact probably wasn't lost on him.