This actually started as a test for texturing the ground. Then I kitbashed the trees in the foreground by using a nice tree trunk and main branches of a free tree model (deleted ugly smaller branches and leaves), and used some nice branch/leaves clusters of another free tree model (deleted the ugly trunk), and created a particle system in 3ds Max using the main branches as particle emitter and the clusters as particle instances. Thus I got a nice lush tree (there are some weird connections, but they aren't visible I hope...). Eventually I thought, the leaves are still too big (happens quite often with 3d tree models), and so I used my own triple leaves texture, which reduced the scale (and increased the number!) of the leaves by a factor of three.
I found some nice character models, retextured them and ran most of the models through Mixamo to pose them.
I had to cheat a bit, since the path tracer still does not render water transparency, so I rendered the area with the water with the legacy (RT) sampler and put it together in Photoshop.