Envirotex lite has a very exothermic reaction and can give off a fair amount of heat with volume, so be careful with thin plastic bits and anything that may melt or warp. It can also "creep" on you. If there is a texture it can crawl up, Sometimes it has on me. Never thought it would creep "uphill" while it dries, but it has on occasion. I'd also reccomend painting anythign you have emerging from the water with the mix first, as to reduce the surface tension when you pour it in. Other than that I really like this product.
Also watch out for dust and cat/dog/girlfriend hair while setting. I usually put my stuff under an upside down box or something to keep crud from falling into it.
Wyrd bases can be very cool on their own:
This water/ripples was done with sculpty and then topped with Envirotex lite
Same product just with paint added to create murkyness.