Originally Posted by Hightower
I mean you can tin the end
True. However, tinning the end of the stripped wire is meant to facilitate soldering. It is not a "marinization" of the cable.
Copper, if exposed to sea water, will rapidly corrode, causing the strands to become brittle. This is noticeable, and somewhat problematic, where the wire is stripped, but is actually more of a problem within the insulation, where you would normally assume there to be no problem. The water wicks up the stranded conductors, and corrodes the strands further up the cable.
Marinized tinned wire has each strand of the wire clad with tin (or a tin/lead alloy; i.e. solder) in order to protect the copper from any water intrusion. This does not mean that you can or should do away without further protection (adhesive lined shrink tubing, dielectric grease, etc.) but rather that the onset of conductor corrosion problems will be somewhat delayed.