Guy,
I personally would not recommend polyester unless you have some type of fume extraction system. The monomer is toxic and will stink up your entire house. There is a fumehood at my work which I used.
What I suggest is that you go to the art shop and get some gloss acrylic medium that you can mix in acrylic paint and tint, and you can pour it in thin layers around your model. The lowest layers should have the most tint and the top layer be completely clear. Be patient and let everything dry before adding more layers. I've seen excellent results this way. The important thing from my canal dio, is that I blew air over it as it dried so that it developed a surface in the same way that 1:1 water does.
Check out model railway forums as they have great ways of simulating water. And also other modelling forums (armorama, migforums), Shep Paine's book on dios etc etc. And try out your techniques on a model that doesn't matter before making a mess of one that does. Experimentation is the only way to find out what works for you.
Good luck.