The intertidal zones indicate the area between low tide and high tide lines.  According to PengHu County Record, the total area in PengHu is 164 square kilometers, 37 more than the area in high tide (127 square kilometers).    The zones are wet and dry alternant areas by high tide and low tide, and most prosperous for marine life and consumer clustering with abundant sun light, nutrition, and micro-planktons, however, with most human interruptions.  Intertidal zones can be divided into (1) tidal zone: with direct sun light and fluctuate temperatures with seasons, a bad environment, small amounts of lives, such as blue-green algae, Ligiidae, and hermit crab; (2) reef zone: with most varies of species which most are algae, bottom inhabiting mollusk, and centipede, with features of dry-resistant and wave resistant with fixing, including green alga, long-leaf seaweed, acorn shell, Liolophura japonica, sea shell, and Saccostrea mordax; (3) tidal pool: the water pool in low tide, with deep or shadow water, and area near low tide line with a variety of sea lives, such as enteromorpha, hermit crab, solider crab, Holothuria atra Jaeger., Holothuria leucospilota, Diadema setosum, Hemicentrotus pulcherriuss, sea shell, small fish, Eucyclogobius newberryi, and Ophiocoma scolopendrina; (4) sand zone:  with bad environment where sea lives are uncovered in strong winds and dangerous under hot sun lights, lives here with high breeding rate and high death rate, such as  Halodule pinifolia (Miki) Hartog, Zannichelliaceae, Halophila ovalis (R.Br.) Hook. f. Hydrocharitaceae, .lpheus brevicristatus de Haan, Alpheus lobidens de Haan, Sea pan, polychaete, Archaster typicus, Portnus pelagicus, and Sanguinolaria acuta; (5) coral zone: coral is the most important biological resources in PengHu sea, and calcium carbonate it makes will form reef.    Less soft coral, stony coral are major types in PengHu inner sea, including Low staghorn coral, Montipora cactus , Pavona decussata , Turbinaria peltata, and Favia speciosa.  In the coral zone, there are lots of fish, shrimp, and sea shells living.  Stones used in traditional PengHu House are coral pieces.  The sea lives in the zones include octopus, Etisus laevimanus, Gonodactylus chiragra, clam, razor clam, and Gymnothorax.