Atlantic bluefin tuna use a mechanism referred to as countercurrent exchange to keep its core muscles warm and prevent the loss of heat when swimming. Counter current exchange is the mechanism in which oxygen enters the blood in fish. Blood flows in the opposite direction to the water that flows over the fish's gills. Fish gills have gill filaments and these filaments have protrusions called lamellae which the water flows over. The lamellae increase the surface area of the gills meaning that there is a larger area for the oxygen to diffuse over. With the counter current exchange system the water is always richer in oxygen than in the blood therefore maintaining the concentration gradient. The oxygen then diffuses into the blood capillaries of the fish.

In the 17th century, the Bishop of Quebec approached his superiors in the Church and asked whether his flock would be permitted to eat beaver meat on Fridays during Lent, despite the fact that meat-eating was forbidden. Since the semi-aquatic rodent was a skilled swimmer, the Church declared that the beaver was a fish. Being a fish, beaver barbeques were permitted throughout Lent. Problem solved! The Church, by the way, also classified another semi-aquatic rodent, the capybara, as a fish for dietary purposes. The critter, the largest rodent in the world, is commonly eaten during Lent in Venezuela.

Due to their extreme environment, humans have not been able to document them properly in the wild. Only a couple of rare underwater pictures have ever been captured. Nearly everything we know is based upon dead blobfish discovered in trawling nets. The photo below is thought to be a Western Blobfish, photographed by an remotely operated underwater vehicle (ROV) at a depth of approx. 1220 m, 70km off Barrow Island, North West Shelf, Western Australia.

The demand for real, sturgeon caviar is always greater than the supply. Female sturgeon only begin producing eggs after seven to 20 years, depending on the species. A beluga can take up to 20 years to reach maturity. A female fish only spawns once every several years. Caspian caviar is the most sought after, but trade in wild-produced caviar is heavily regulated by Cites—Convention on International Trade in Endangered Species—in order to protect the critically endangered species of sturgeon, making it extremely difficult to come by. When caviar is lightly salted it allows the naturally nutty flavors to shine through. This type of caviar, known as "malossol" is the best quality caviar but it is good for only a few weeks. Every package of caviar is the result of a detailed, manual harvesting process. Eggs are carefully extracted from the fish, washed, and prepared by hand to ensure the eggs retain their quality. The entire collection of up to two million eggs is analyzed and any bad eggs are discarded.

A Nor'easter is a storm along the East Coast of North America, so called because the winds over the coastal area are typically from the northeast. These storms may occur at any time of year but are most frequent and most violent between September and April. Some well known Nor'easters include the notorious Blizzard of 1888, the "Ash Wednesday" storm of March 1962, the New England Blizzard of February 1978, the March 1993 "Superstorm" and the recent Boston snowstorms of January and February 2015. Past Nor'easters have been responsible for billions of dollars in damage, severe economic, transportation and human disruption, and in some cases, disastrous coastal flooding. Damage from the worst storms can exceed a billion dollars. During winter, the polar jet stream transports cold Arctic air southward across the plains of Canada and the United States, then eastward toward the Atlantic Ocean where warm air from the Gulf of Mexico and the Atlantic tries to move northward. The warm waters of the Gulf Stream help keep the coastal waters relatively mild during the winter, which in turn helps warm the cold winter air over the water. This difference in temperature between the warm air over the water and cold Arctic air over the land is the fuel that feeds Nor'easters.

Coral reefs can be divided into three types: fringing reefs, barrier reefs, and atolls. Fringing reefs are close to shore, whereas a barrier reef will lie further out to sea. Often, atolls will be mistaken for islands because they are so large and generally appear on the rim of a lagoon.

Red algae living on the Greenland ice sheet account for 5 to 10 per cent of the ice sheet's shrinkage. The algae turn the snow pink when the slightest melt occurs. This "watermelon snow" absorbs light, which heats the snow, and creates a feedback loop that hastens the disappearance of snow.

Kelp harvesting during World War I peaked in 1919 when 400,000 wet tons were used to make potash for gunpowder and fertilizer. In the 1930s the food, pharmaceutical, and scientific communities began extracting algin, a thickening, stabilizing, suspending, and gelling agent. Algin is an additive used in a wide variety of dairy products, frozen foods, cakes, puddings, salad dressings, shampoos, and toothpastes. It smoothes and thickens ice cream, emulsifies salad dressing, and keeps pigments uniformly mixed in paints and cosmetics. Additionally, some mariculture farms hand-harvest kelp to feed abalone. In the 1980's alone, kelp harvesting supported an industry worth more than $40 million a year, and in 1993, more than 4,700 wet tons of kelp were extracted from the Monterey Bay National Marine Sanctuary.

Certain species of tropical fish carry fertilised eggs in their mouths and continue to hold the babies there for a while after they hatch.This can be found in both paternal and maternal members of the species. The following section will focus primarily on mouthbrooding cichlids from the African Rift Valley from the lakes Malawi and Tanganyika. Once the babies have hatched they will feed on the remnants of the yolk for the following 25 days or so, after which the female will gather food in order to feed the young whilst they remain in her mouth. Babies that are fed ‘bucally' this way develop to be far more durable, faster and heavier than fry and although mouthbrooding provides a smaller batch of babies than other methods, they are stronger and will be more likely to reach maturity.

Because of their large, skinless pectoral fins, hawkfishes are able to perch upon fire corals without incurring harm. Actually hydrozoans rather than true corals, fire corals possess stinging cells (nematocysts), which would normally prevent close contact. Afforded some degree of protection by their living perches, hawkfishes seek the high ground of the reef, where they warily survey their surroundings like hawks. This is said to have inspired their common name.