One caution I always point out is that if you dont treat a deck it will absorb more moisture which in turn increases the likelihood that it will become slippery when wet. Caution should always be taken when walking on wet decking.
A large Deck incorporating a pool
This second example is built using a harder American timber
This next picture shows the frame work under the previous deck construction
The next picture is of a much smaller deck in my own garden
A raised deck with rails