Your render settings look pretty reasonable, even with soft shadows (when using Defer All and Robust Adaptive Sampling, soft shadows have a more moderate impact on render time). You are also not using path tracing here (Path Tracing On Surfaces set to 0), so the Path Tracing settings (Ray Depth, etc.) don't matter anyway. If water was the biggest render time hit, transparency may well be the reason. But again I would encourage you to share an image of your actual scene, even now that you've successfully rendered it. That can tell us a lot. We also need to know your system specs (CPU, memory, OS) to better judge relative performance.
So overall your settings seem pretty normal to me. What's missing from the consideration would be things like atmosphere and cloud samples/quality, which can also have a big impact.
- Oshyan