Factory trawler: A large ship equipped to catch, clean and freeze fish for market.

Family: In biology, a category that's part of the scientific system for grouping together related plants, animals, and other organisms (kingdom, phylum, class, order, family, genus, species). Family is the category that ranks below an order and above a genus.

Fat innkeeper worm: A wormlike invertebrate that burrows in mud; it's called the innkeeper because many other small animals come to live in its burrow.

Fault: A break in the rocks of the earth's crust along which movement may occur, causing earthquakes.

Feather-duster worm: A marine worm that lives in a leathery tube and sticks out a bright orange or purple crown of soft, feathery gills. When disturbed, it pulls the gills into the tube lightning-fast.

Feces: Solid waste that passes out of an animal's digestive tract.

Fecundity: Number of eggs an animal produces each reproductive cycle; the potential capacity of an organism or population.

Feral: Wild, used to describe animals that are usually not domesticated, like cats or pigs.

Fertilisation: The process in which the nuclei of a sperm and ovum join to make a new living thing.

Fertilisers: Chemical used to make plants grow faster.

Fetch: The distance over the water's surface that the wind blows to generate waves.

Fillet: To cut a slice off the side of a fish.

Filter feeder: An animal that eats by filtering or straining small particles of food from the water.

Filtration: Separation out of wastes and turbid water (in aquariums).

Fins: In snorkelling or diving, footwear used to propel body forward. Sometimes called flippers.

Fiord: An estuary that occurs in a deep, narrow, drowned valley, originally formed by glaciers.

First aid: Immediate help given to a person who has been injured before they go to hospital.

First order consumer: Animal that eats a producer.

Fisheries management: The effort to regulate where, when and how people fish, and how many fish they catch, to protect fish populations so that people can continue to fish. Most fisheries management is done by government agencies such as the U.S. National Marine Fisheries Service.

Fishery: The organized harvest of a certain species of fish or shellfish.

Fish pens: Large tough plastic holding tanks for fish grown in aquaculture.

Fishing pressure: The amount of fishing for a certain species of fish or shellfish. If there's heavy fishing pressure on sharks, it means that lots of sharks are being caught by fishers.

Flares: Safety devices that are used to attract attention at sea. Can use smoke or parachute.

Flatfishes: A general term for fishes like flounder, sole and halibut that are flattened for life on the seafloor.

Flat porcelain crab: A small crab with a smooth, shiny shell that lives in the intertidal zone.

Floating platforms: Structures used by tour operators to moor charter vessels on a reef also known as pontoons.

Flounder: A fish with a flattened body adapted for life on the seafloor.

Flukes: The flat tail flippers of a whale or other marine mammal.

Food chain: The relationship between plants and animals that shows who eats what. Energy is transferred from one organism to another through the food chain.

Food web: Interconnected food chains in a community; an abstract representation of the various pathways of energy flow through populations in a community.

Forward: The front section of a boat. To move ahead.

Fouling organisms: An assortment of benthic organism (such as barnacles, sponges and algae) that settle on boats, clog underwater pipes, and generally cause problems to marine vessels.

Freeboard: The vertical distance from the gunwale of a boat to the waterline measured amidships.

Frond: A long, feathery leaf, or the leaflike blade of a kelp plant or other sea plant.

Fungal: Having to do with a mold, mushroom or other fungus.