The World Below Your Boat

By Susan Shingledecker

As boaters, we become very familiar with the water's surface and its various waypoints and landmarks. Let's take a tour of the magnificent ecosystems living under our boats, learn how they're doing, and find out the safest ways to get a closer look.

Coral Reefs

Coral reefs may have you thinking of warm tropical waters off Florida, the Gulf Coast, or Hawaii, but coral can be found in cold waters as well. According to NOAA , shallow-water coral reefs occupy 110,000 square miles of sea floor, approximately the size of Nevada, accounting for less than 0.015 percent of the ocean floor, but they're home to more than 25 percent of the ocean's biodiversity. Coral reefs provide tremendous economic benefit through their value for fisheries, tourism, medical research, storm protection, and other environmental services. Coral reefs are currently under threat from climate change, unsustainable fishing practices, and land-based pollution.

Photo of a coral reef

Kelp Forests

California is famous for its kelp forests. You're likely to encounter them on a cruise out to Catalina Island, but did you know there are kelp forests on the East Coast as well? Kelp is one of the fastest growing plants on each coast, growing a couple of feet a day in ideal conditions. Kelp grows in areas with rocky substrate in depths up to about 90 feet. Kelp needs clear waters to allow sunlight to penetrate the water column. Like a typical forest, kelp provides habitat for a variety of species. While kelp beds provide excellent fish habitat, never run your boat through kelp beds. They often look like flat patches on the water because the vegetation calms the wind and wave action at the water's surface. The dense fibers can wrap around your running gear; broken strands can clog water intakes; and long kelp strands can entangle novice divers.

Seagrass Beds

Seagrass beds are areas of submerged plants found growing in bays, lagoons, and shallow coastal waters. These plants anchor to the bottom with a rugged root structure allowing them to withstand strong currents and waves, and act as an excellent buffer during extreme storm events. Seagrass can be found as far north as Alaska and well into the tropics to the equator. They're considered the foundation of many coastal ecosystems, providing essential habitat and nursery areas for several species of fish. Between 70 and 90 percent of commercial fish spend part of their life in a seagrass habitat.

Photo of a seagrass bed with a fish swimming through it

Deep Boulder Reefs

Deep boulder reefs off the Massachusetts and Maine coasts disprove the theory that the sea floor in colder northern waters is barren and brown. The Gulf of Maine is known for its colorful anemone and sea stars, in addition to lobster. While these underwater rocky habitats are not well mapped, they exist throughout much of the Northeast. Deep rocky habitats are more likely to be inhabited by invertebrates such as horse mussels, sponges, sea cucumbers, and anemones as opposed to kelp. These ecosystems are also home to popular fish species such as cod. Don't anchor amid rocks or boulders. Better to bring your dinghy, snorkel, mask, and flippers over for a closer look at this beautiful ecosystem.

Photo of a deep boulder reef home to horse mussels, sponges, sea cucumbers, and anemones

Shellfish Beds

From oyster beds in Washington state, Gulf of Mexico, and Chesapeake Bay, to scallop, clam, and mussel beds in New England, New York, and other areas, shellfish beds are common in many parts of the country.

Photo of a shellfish bed

Native shellfish play a vital economic role in many fisheries, and act as important filter feeders providing improved water clarity, helping to keep the entire ecosystem in balance. Many shellfish such as oysters and mussels need a hard surface for spat or juveniles to attach and grow, while species such as clams are found in mud flats. 

— Published: April/May 2012

Please Take Care

Coral reefs and seagrass beds are both economically important and easily damaged. The federal government and states such as Hawaii and Florida have taken steps in recent years to strengthen laws that help protect these important resources, which include seeking to recover damages as well as increasing the fines that can be levied against boaters who damage marine environments. Fines in Florida for damaging a seagrass bed start at $50 and can increase to $1,000 or more for multiple offenses. If you run aground in a marine sanctuary, such as the Florida Keys National Marine Sanctuary, the feds could send you a bill to pay for restoration of the affected area. This past December, seven boaters were assessed an average of $6,300 for damages to seagrass beds in federal sanctuaries.

Photo of children fishing off a boat

Submerged seagrass beds can be difficult to see on the water. If you're boating in shallow areas with known seagrass beds, stay in marked channels. Wear polarized sunglasses to reduce glare and allow you to see shallow areas and the beds. Know the depth where you're boating and your boat's draft. If you see a muddy or cloudy wake, tilt your motor up and head slowly for deeper water. If you run aground, turn off your engine and use a boat hook or similar object to carefully pole your way back to the channel.

Damaging coral reefs can be expensive as well. Fines of up to $250,000 and unlimited compensatory damages are possible. Hawaii, home to more than 80 percent of the coral reefs in the U.S., fines offenders for the costs of restoring corals damaged in groundings. In 2009, a tourboat operator was fined $400,000 after one of their dive boats sank, damaging reefs off Molokai.

Exploring coral reefs with snorkel or scuba gear can be a great experience. Use mooring buoys if available. If not, anchor your boat far from the reef, and explore with your dinghy. To anchor the dinghy near a reef, use a mask to check the sea floor for a clear, sandy area. Carefully lower your anchor, check that it's well set and won't drag, and that your chain and line won't touch the coral even if your dinghy swings 180 degrees.



BoatUS Magazine Is A Benefit Of BoatUS Membership

Membership Also Provides:

  • Subscription to the print version of BoatUS Magazine
  • 4% back on purchases from West Marine stores or online at
  • Discounts on fuel, transient slips, repairs and more at over 1,000 businesses
  • Deals on cruises, charters, car rentals, hotel stays and more ...
  • All For Only $24 A Year!

Join Today!