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.
Ewens Ponds
High underwater visibility, the presence of rare and interesting fish, invertebrates and plants and the ponds' unique photographic potential have made them popular with scuba divers. Of particular interest in these clear waters is the actual observation of photosynthesis - aquatic plants can be seen releasing thin trails of bubbles as they convert carbon dioxide into oxygen. However divers are prohibited from entering caves or crevices on the pond beds and strongly discouraged from disturbing the silt layer as the resulting turbidity may harm plant life. Divers enter at the First Pond, drift with the current through the First Race to the Second Pond, and then continue through the Second Race to the Third Pond before exiting the water via a ladder there. However, some divers (especially snorkellers) occasionally attempt to vigorously swim upstream through the races to return to Ponds One or Two, thereby disturbing the water plants lining the races, and this practice is strongly discouraged by the diving community. The general water temperature of the ponds is around 15 °C (60 °F).