More dynamism is Waterfalls, Rivers, and water in general. Not only are rivers more "realistic" looking, in that they fall from a source and flow into the ocean eventually or what not, but also there is an actual flow to the water.
Now whether or not the water blocks are finite or infinite doesn't matter. The idea is that every water block has a direction its flowing, and a speed. So there might be rapids or it might be flowing slowly. Maybe you can tell from the texture or maybe you'll see where the fish or some particles flow. The river itself should flow in a direction from the source of the river down to the ocean or whatever.
I imagine the game can't generate the whole river system at once, rather starting with a random middle of it, so it would need to pick a direction. Probably all rivers would be heading the same direction, either north or south, depending on where you are on the planet. Either way, it'll be flowing downhill.
Lakes might be calm, but there might still be a flow to them. Whether rivers flow into them or not. This could create small waves. Definitely on an ocean it should create larger waves that follow the tides and the moon.
If two currents of opposite directions are flowing into each other, it can create a whirlpool. Or not if that's too hard to code.
Waterfalls when flowing down a cliff could dissipate into particles or the like to simulate the look of a waterfall, while there are perhaps invisible blocks to identify where the water is flowing. If it's in particles, when you turn off the particles render it just shows the blocks themselves. But the blocks could be thin and vertically aligned, maybe shrink wrapped around the blocks they're flowing around.
Maybe there are also puddles which could form from tides or after rain which are just like a thin slab of water on the ground.