here’s an idea
John Dowd, in his book “Sea kayaking” suggests keeping an orange or black plastic bag handy at all times, to put on the paddle and wave around. Not sure about the black but an orange bag to wave around sounds like one of the better ideas. Or paint your paddle orange if you regularly paddle in such unfriendly conditions.
"Paddle Flash"
The “flash” on the water from yellow and orange paddles can be readily seen way before the boat. White not so much, black none.
Give Salty Some Space 
Yah give ol salty some room to slalom around the bouys on the Hudson
http://www.youtube.com/watch?v=d4gAOiWq1x8
(u need to watch it in 1080 to see the red buoys)
Air horn…or two