Daichii Bleeding Bait Hooks
and
  Cajun Line
 

Cajun Line is transparent, hence the red color we see is really a clear "see-through". 

Daiichi Bleeding Bait Hooks are opaque and reflect the red color                   at great depths. Red line does not really "disappear"...         
it simply changes color.

Its transparency allows "see through".

If red really disappeared, our Navy Submarines wouldn't be black - they'd be red. Remember... Fish can see UV colors we can't see and do recognize red as a feeding signal in depths over 170'. I've looked at 12 pound Cajun Line under water and it's impossible to see while the Daiichi Bleeding Bait Hook is very visible.

  "Transparent versus Opaque"  
<a href="http://www.apple.com/quicktime/download/">Quicktime Required</a>
Quicktime Required
Check out this
QuickTime Video
on Bleeding Bait Hooks!