It's the end result of a buffer, merge, bugffer and Chaikin Smoothing process in PostGIS. It's almost perfect however I'd like to remove some of the "fissures". If I could get the shape to have the boundary like the red line below it would be great. Ideally something I can do in postGIS.
There is a function made exactly for this problem: ST_ConcaveHull
ST_Simplify can work, but it is not exactly the best option depending of the situation (it's not really what it's made for, and you will easily lose the details of the boundaries of your polygone while still having holes).