I dont' SvS or PvP... too competitive for my way of playing.
But a friend of mine relayed some info to me regarding his experience with "seeing the enemy" on board their ships.
"Well, one thing to add on this topic... the "Character Detail Level" has to be on HIGH or else enemies are invisible at sea.
In SvS, grape shot is 100% ineffective when the enemies are invisible.
On my computer, to play SvS, I have to have character detail level set to "LOW" or the lag is intolerable."
This was the same friend who was purposely trying to hit me with grape shot just to see what it would take to take me out.
Hope that gives you some info...