Upwelling
The major upwellings in the ocean are associated with the divergence of currents that bring deeper, colder, nutrient rich waters to the surface. There are at least five types of upwelling: coastal upwelling, large-scale wind-driven upwelling in the ocean interior, upwelling associated with eddies, topographically-associated upwelling, and broad-diffusive upwelling in the ocean interior.
Whitewater
A boulder or ledge in the middle of a river or near the side can obstruct the flow of the river, and can also create a "pillow"; when water flows backwards upstream of the obstruction, or a "pour over" (over the boulder); and "hydraulics" or "holes" where the river flows back on itself—perhaps back under the drop—often with fearful results for those caught in its grasp. (Holes, or hydraulics, are so-called because their foamy, aerated water provides less buoyancy and can feel like an actual hole in the river surface.) If the flow passes next to the obstruction, an eddy may form behind the obstruction; although eddies are typically sheltered areas where boaters can stop to rest, scout or leave the main current, they may be swirling and whirlpool-like. As with hydraulics (which pull "downward" rather than to the side and are essentially eddies turned at a 90-degree angle), the power of eddies increases with the flow rate.