usually start at about 12'. working down to 14' if i am not getting many bites. early morning or late in evening i would start at 10' and work up to 6'. pollack and other fish will often rise up in water under cover of feint light. don't take this as gospel though! i have caught them fishing 3' deep and others at over 25'! great way to fish, enjoy my friend!
forgot to say, a bait floating about just above the kelp is destined to be scoffed. find the depth to the kelp by moving your stop knot deeper/ shallower depending. don't tie your hook on until after you do this! the float will lie flat when the lead is resting on the kelp. so shallow it up until you are fishing at desired depth above the kelp.
If you fish into the darkness you can have great sport by attatching a starlite to the top of your float.Simply press it in to the polystyrene so it makes a dent and then secure well with bait elastic or powergum.I have had great sport over a similar kelpy mark using this method.Good Luck!!