In the middle of the Atlantic ocean, with a salinity of 3.2%, a VLF signal will penetrate down to a depth of 10-20 meter, barely periscope-depth for a modern large scale submarine.

• 在大西洋中部，海水的盐度为3.；2%25，甚低频无线电信号可以穿透到海面下10~20米的深度，几乎就是现代大型潜艇的潜望镜深度。