I played a bunch with a 10 year old machine and had to minimize a lot of my settings to get a steady 30 FPS, but anytime I went near areas I had heavily changed the area geometry for (with lots of digging), the game took a huge hit while it loaded the area. After it was done, it was choppy at best. In my experience, the mountain biome (when it wasn't storming) seemed to be the most optimized, where I could frequently get 60 fps.

I've since upgraded to a very powerful modern machine and I've been able to run the game perfectly on full settings and twice the resolution. I've never had an issue with large bodies of water being the cause of my performance issues, either with this machine or my old one. My starting point and first home was on the ocean front, and I've had several sailing expeditions with no issue.