When using the other GF9 water product (can't remember what it is called off the top of my head but it is the one which is made up of little plastic pellets that you melt and then pour into place to form large bodies of water) - make sure you have heated it well past melting point.
I melted it so that it was runny and liquidy and then went to pour it out - it did not retain enough heat to remain pourable for more than a few seconds and by the time it had touched the surface I was pouring onto it had started to harden again. I had to sit for ages with a hairdryer (kinda worked but was not very good) and a lighter (better, but it is a naked flame - not a good thing) to get it to flow into place.
If you are using this stuff a heat gun might be a good investment.
Edit: Oh, and make sure if you are having to reheat the water on the base, direct any sources of heat you use away from any plastic models on the base as they will get melted