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).
One of the solutions to your problem
Create an external buffer by running the script:
create table table_buf_exter as
SELECT ST_Buffer((ST_MakePolygon(ST_ExteriorRing(ST_Buffer((geom),0.007)))),-0.007) geom
Set the value of the buffer, so that they cover the width of the fine parts.
good luck in good deeds ...