Date: 06/03/2010 8:47 PM Title: Gatchaman Episode - Part I
For those who don't know: Jinpei is wearing a 'fundoshi' in the speedboat. It isn't seen much anymore, but this was what Japanese men wore before the introduction of Western-style underwear.
Sonar works by transmitting soundwaves at certain frequencies, which bounce off of objects. By analyzing the return, the sonar operator determines what's in the path.
Sub-hunting details are Top Secret.