SO ENDS this first of two weekends contemplating the return to the sea of the seagrasses. Like the whales, these organisms have made this challenging reversal by numerous genetic, biochemical, anatomic, and physiological modifications, rendering them totally different from the creatures that first emerged from the sea to dry land. Their return was not simply a reversal of status, a return to how they were. It was more strenuous — by far — than the twisting of a vertical flatfish face horizontal.