I don't know if anybody already noticed this.
I was send to patrol near the Marshall islands. I was cruising between the islands and I saw large numbers of ships I was very shallow waters so I surfaced.
When I approached I sudddenly heared a bing bang and futher investigations learned me that there was a net all around those Islands. So I sailed along side the net looking for an opening. there was one close to the island "Kwajalein" But do it submerged as there ar coastalk batteries (trust me I learned the hard way

)
Once your inside the fun begins. All ships are stationary so it's really a turkey shoot.
The 2 dark pool are deep water, keep them in mind when planes are searching fotr you...those are the only 2 places where you'll be able to dive deep.
Happy hunting