Most Iray HDRI environment sets don't allow the depth of field use easily and directly out of the box.
UltraHD Iray HDRI With DOF - The lake does!
You won't have to tweak anything as all the presets are there for you to just click and render.
With UltraHD Iray HDRI With DOF - Fishing huts, you'll get 1 ultra HD (up to 16K) custom-made environment with or without the depth of field presets. This environment is a rocky beaches with small typical wooden fishing huts. In France, they are known as "Carrelets". The carrelets are in fact the nets fishermen use on high tides to get the prey but also the name of a fish.
This environment is provided in 4 different resolutions based on your needs and computer capabilities:

16000 x 8000
8000 x 4000
4000 x 2000
2000 x 1000

Each resolution is provided with or without the depth of field capability.
You can also use the DOF-enabled environment and not activate the DOF of the camera for a third and different effect. Based on your need, click on the wanted resolution, click on the wanted depth of field option, click on the wanted dome rotation preset, and you're good to render.
Take advantage of the HDR environment SPEED (versus the full 3D environment that is way slower to render) with an optimized depth of field!