Things You'll Need
Clear casting resin
Dioramas are scale representations of a scene from a book, film or history. They are normally about the size of a shoe box and are commonly used as an arts and crafts project at school. Cardboard, plastic or a craft wood, like balsa, are used to fashion buildings, people and other elements, but water is a problem, as liquid would ruin other models. Instead of using the real thing, you can use resin to create a solid substance that looks like real water. You can purchase clear casting resin from an arts store. This is not cheap -- around $15 for 16 ounces -- but it is very effective.
Decide what color the water needs to be. South pacific islands need clear blue water, whereas city rivers are more brown and grey. Enamel paint mixes best with the resin.
Make sure all elements of the diorama are glued down securely, unless they are going on the water, and remove all dust, as this will adversely effect the resin.
Dam off the area where the water is going with balsa wood if necessary. This will stop the water from getting into areas where it is not wanted. Alternatively, just pour a little at a time.
Mix some of the resin with the catalyst, saving some for later. The catalyst is a reactionary agent that allows the resin to set hard. It will come with the resin kit. Then, add small amounts of each color of paint when mixing the resin to slowly build up the color until it is slightly darker than you want it to be. Add the paint slowly; it is possible to add more, but not to take away.
Pour the resin into the required areas of the diorama and leave to dry as per manufacturer's guidelines.
Mix some more resin with less paint than before and pour this on top of the dried resin. This will give the look of depth to the water. As before add small amounts of paint at a time. This will require just enough to add a tint to the resin, but not fully color it.
Use a small piece of balsa wood or paint brush to add effects to the top of the water. If it is the sea, drag the wood toward the beach to create waves. If it is a river, make small flecks to indicate a current.
Allow the resin to dry and then glue objects like boats onto the water as required.
Do this in a well-ventilated area and always wear the face mask. Resin is toxic in liquid form.
Really think about what you are doing before attempting this, as it is impossible to reverse the process. Be organized and have everything to hand, as once you start, you'll need to think and act quickly.