Hi
I was talking about the sand bars (West Pole and East Winner) which are formed at the two harbour mouths and extend outside. These areas are unexploited but hold an amazing head of bass. The channels and gulleys I'm talking about are the ones outside the mouths and are mainly sand with some kelp (which develops through the summer) in the more protected areas in the lee of the tide.
You need to recce on a big Spring to see what I mean. Park at the end of Southwood Rd. (Ignore the word Havant on this map!!!! It's SE Hayling)
http://sthwood.notlong.com
Zoom back two notches to see where you are.
I don't know much about the Thorney to Bosham stretch of the harbour, but bear in mind that water clarity is much better on the flood and over HW than on the ebb. I know they fly fish for bass at the tip of Thorney, but access is difficult.
Anywhere inside the harbour mouths is mud and silt.
Hope that helps
Ada