My knowledge of this is zero. I understand it better now after reading this. My biggest regret fishing wise is that I never learnt how to dive. A good life should have at least a regret or two 

On Saturday Shelly and I took her brother out for a fish (he's very keen and knows his stuff).  We covered a lot of ground but it was interesting talking to him when we stopped at places I had previously spent time swimming round with a speargun.  I explained the details of the underwater terrain, what it did to current in certain places and how it all impacted fish behaviour / where the fish were (e.g. there are some bricks that don't show up on charts but are enough to influence things and some other bricks that are on the charts).  It was an interesting conversation and he kept quizing me.