Scientific Anglers Sonar Sink 25 Cold Water. Sinking-Head fly line for Cold Water water. The SONAR series takes your fly and puts it right in front of the fish. Whether you're throwing streamers for trout, big flies for muskie, or even fishing stillwaters, we have the perfect sinking line for you. Get down, and stay down, with SONAR. 25' extra-fast sinking head with handling lineReplaces Mastery Wet Tip ExpressAn excellent streamer line for troutLow tangle design increases shooting distanceFloating running lineSuper Fast Sink: 4.0 - 8.0 ips, sinks 4' - 15'For Cold Waterwater applicationsBraided multifilament coreWelded loops