NAUI Master Scuba Diver The Diving Environment the plant from the roots. They are all popularly called seaweeds, which consist of a group of non-flowering plants properly called algae. The three most common groups are green algae, brown algae, and red algae. To remain in one place, these plants attach to the bottom with a root-like structure called a holdfast. Seaweedcovered rocks can be very slippery, affecting entries and exits. Divers can also become entangled in algae, but this should not pose a serious threat. Panic is the diver’s worst foe in a plant entanglement situation. By simply remaining calm and thinking, a diver can usually get free of such an entanglement quickly and easily, or with a bit of buddy assistance. Kelp is the name for a group of large brown algae found in temperate waters. Forests of kelp on the western coast of the United States grow up to the surface from depths of more than 30 m (100 ft) and are abound with life just like the forests on land (figure 2-19). Like their terrestrial counterparts, these undersea forests have a beauty that is unique. A tough holdfast anchors the algae to the bottom, while gas bladders called pneumatocysts float groups of stipes (strands) to the surface, where the kelp spreads out to form a thick, floating canopy. It is much easier to swim under the canopy than through it at the surface, so experienced kelp divers save enough air to return to their exit point beneath the canopy at the end of a dive. Surf grass or eel grass are flowering plants found in the surf zone. Entanglement in these plants is not common. Surge may wash it over you, causing apprehension, but if you are calm and patient, the grass will clear when the surge reverses direction. Freshwater plants such as water lilies or hydrilla can grow densely in some inland lakes and streams. You can become entangled in the plants and surfacing can be difficult. A calm, controlled procedure of freeing yourself is the best solution to an entanglement problem. In some states it is illegal to remove and transport certain plants from lakes. All equipment must be clear of weeds before packing and transporting it. INVERTEBRATES Approximately 97% of all animal species are invertebrates, or animals without a backbone. These include relatively simple organisms like sponges, jellyfish, and corals, up through the worms, mollusks (snails, clams, and octopus), arthropods (shrimps, lobster, and crabs), and echinoderms (seastars and sea urchins). It is beyond the scope of this book to describe the thousands of species of invertebrates that live in the world’s oceans and fresh waters, but you are encouraged to study further. Only the potentially hazardous types will be discussed here. VERTEBRATES Fishes The fishes are the oldest and simplest of all living vertebrates (animals with backbones). They are very important economically and are a vital source of protein for millions of people. They are divided into three major groups: the jawless fishes, bony fishes, and cartilaginous fishes such as sharks, skates, and rays. Birds and Mammals Seabirds, birds, and mammals are conspicuous members of the oceans and fresh water regions of the 50 FIGURE 2-19. KELP FOREST
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