Flooding is a regular occurrence these days and there are still opportunities for some top quality fishing in the dirty water. Fish still need to eat regardless of the visibility and the important thing to remember is that all the fresh water will be in the top layer of water, there will still be salt water towards the bottom especially in deep holes. Most predatory fish will take advantage of the dirty water by ambushing prey as it is flushed out of canals and rivers. The seaway itself provides an excellent hunting ground for predators after a flood due to its depth and strong tidal flows. The deep hole at the end of the north wall is particularly good as it enables fish to rest in the salt water on the bottom and dash up to the surface through the fresh to grab some food. Fish like Mulloway, Tailor and the various Trevally species have no problem hunting in dirty water but they tend to do so only at a time that suits them. This may be at the start of a run out or start of a run in tide.
For a look at a report made shortly after a flood you can look at this one from last year: http://seawayfishing.info/2012/02/27/seaway-report-27th-february-2011/