This was a three second exposure (with about 10 stops of neutral density). The sun was behind the clouds and just above the center of the frame; the lens required careful flagging to avoid glare.

The rendering of water, especially in the sea, differs greatly with exposure. 30 seconds looks quite different from 3 seconds, which is just as different from 1/30 sec, which is different from 1/1000 sec. About 1/30 sec renders roughly the way our vision does; anything else requires a camera to see.