I guess towed arrays come in many different forms, but the ones I've seen were in tubes filled with a paraffin-type substance to give them neutral buoyancy.
Absolutely right! However if you look at the device used it looked very much like a single hydrophone.
The American detectors are being towed by HMS Echo and HMAS Success. HMS Echo has sidescan sonar and specialises in ocean survey including sea bed. She has been used extensively in the Mediterranean (agreed much shallower) to successfully find wrecks.