Shark liver oil is rich in alkylglycerols, which are naturally found in mother's milk and in bone marrow. It also contains pristane, squalene, vitamins A, D, omega-3 fatty acids, triglycerides, glycerol ethers, and fatty alcohols.
Bermudians rely on unique shark-oil based "barometers" to predict storms and other severe weather, even though electronic meteorological facilities are available. Long ago local St. David's Islanders cooked a shark in its own liver oil. After being melted down in the hot sun, it was poured into a soda (carbonated beverage) bottle and hung outside. The appearance of the oil altered consistently with changes in the weather. From that time on, bottles of shark oil began appearing on walls or terraces.
Local practitioners of the art today say that a reliable way of prediccting the weather is to hang one of these bottles outdoors, then read how the shark oil settles or remains cloudy. Some old timers still check shark oil before going into deep waters. There are dozens of theories regarding why shark oil changes with the climate and whether it is an effective means of reading barometric pressure. The theory that carries the most weight is that electrical changes in the atmosphere affect the shark's liver and alert the shark to move out to deeper water before a bad storm. The oil retains this function when removed and the change is visible; the oil switches from a clear golden color like cooking oil to a milky white.