Below are shots of the retopologised mesh which has been fully UV mapped within Maya. I did the retopology in Maya and not Zbrush because I personally find the tools for retopo in zbrush quite basic and tedious. What I did for the retopology was drop down a few subdivision levels in zbrush, take the lvl 2 mesh into maya, delete the areas I wanted to redo and then create new loops. This worked out quite well and saved me alot of time.
I redid most of the head and parts of the fins as they needed fixing, and I spoke to Clym about how complex the topology should be. We actually agreed since the deformations will not be that extreme, the changes I had already done were sufficient. With that sorted I then proceeded onto the UV mapping which I did myself in maya. I did try to use UV master in zbrush but the results it gave me were not upto the quality I was after, so I decided to do it myself within Maya. As this is one of my specialist areas I blazed through this with no problems. The UV map itself is near perfect I would say, as there is close to no stretching or problem areas.
What I did next was reimport this mesh into the correct subdiv level in zbrush and refined the model as it needed a little tweaking.