f you walk along the seashore on a bright summer day, you will feel the sun warm on your head and the sea spray cool on your cheeks, but you may see nothing more at all except an occasional gull overhead-or the sandpipers that race the waves at your feet. Some strange and wonderful things happen where the land meets the sea. But many seashore creatures are hard to see unless you know where to look. Some can be found in shells, some in plants,...