Atolls

[Crannogman]

I just completed a surprisingly rewarding patrol in the Marshalls-Gilberts in early 1943. I figured command was trying to kick me into a backwater for almost losing a brand new sub on my last patrol.
Turns out it was a bonanza; while touring the atolls, I encountered and sank almost a dozen 5000-ton freighters, in addition to an equal number of smaller ships crusing the seas or lying at anchor in the various lagoons. This was with 1.5, RSRDC, OTC, and NMMO (airbases); it helped that there was basically no air cover in the area, though most of my attacks took place at night and/or in rain.

I found it interesting that the different atolls' coral reefs were modeled differently.
At Kwajalein and Maloelap, anti-torpedo/submarine nets encircled the lagoons completely (near as I could tell). At first I thought to approach these surfaced and try to slide my whole boat over, or else fire my torpedoes across the top; unfortunately, the areas closest to the ships tended to be covered by shore batteries. Further investigation revealed that some of the nets had taken "shortcuts" over small channels of deep water, and I was able to get under them at 200ft; this was easy at Kwajalein, but Maloelap's was not far off the shelf and required some bottom-hugging.
At Jaluit, the lagoon was ringed by land maybe 100y wide and 50ft high. There were a couple low places it seemed that I might slide across, but might just-as-easy be grounded and lost. Fortunately, the ships inside (I guess they were built there) were close enough that I could see their mastheads above the dunes and shell them effectively.
I made a fruitless excursion to Truk as well, whose lagoon had been much more attentively modelled, with nice shoals & shoals and a few channels; however, the active subchasers and aircraft made it seem hardly worth the bother, especially with such an unprotected bounty so much more convenient to home.

[CCIP]

Some very nice observations

I've seen much of the same, although I tend not to get close to harbors or atolls. By and large, they're not defended, BUT you want to be careful because every other one there are some pretty extensive minefields and nets.

[merc4ulfate]

I have found deep water under nets before as well. It isn't so pleasant to try to go over them however.

[SSI01]

A question or two related to those articles in the water:

Does the stock game show the actual antisubmarine net and the mines in the antisubmarine minefields?

Is there a mod that accurately simulates usage of the high-freq FM sonar issued to boats late in the war for detecting submerged minefields?

I know one or two boats were outfitted with this gear when their patrol orders specified they were to transit certain waters that were likely to be mined. Prior to going on war patrol the sonar operators on these boats were put through some training involving being on a surface ship that was outfitted with the HF sonar and that sailed through an inert minefield so they could become familiar with the various indications the gear gave (the noise made by the gear when mines were detected was a tone known to the sonar techs as "hell's bells"). I'm sure that was professionally interesting while it was going on, but it must have become downright engrossing when that sonar was used for real when transiting waters suspected of having been mined. This had to be vacuum-tube technology, primitive in the extreme, and should give pause to anyone reading about it and the chances the crews were taking when utilizing the gear.

[merc4ulfate]

Answer :

No

and No since it's use would be rather unrealistic in that it was not available to 99.99 % of skippers.