A hydrofoil is a foil which operates in water. They are similar in appearance and purpose to airfoils.

Hydrofoils can be artificial, such as the rudder or keel on a boat, the diving planes on a submarine, a surfboard fin, or occur naturally, as with fish fins, the flippers of aquatic mammals, the wings of swimming seabirds, or other creatures like the sand dollar.

The term "hydrofoil" is commonly used for the wing-like structure mounted on struts below the hull of a variety of boat (see illustration), which lifts the boat out of the water during forward motion, in order to reduce hull drag. As a synecdoche, the term "hydrofoil" is often used to refer to boat that utilizes hydrofoil technology in this way. Most of this article is about this type of hydrofoil.

As a hydrofoil-equipped watercraft increases in speed, the hydrofoil elements below the hull(s) develop enough lift to raise the hull up and out of the water. This results in a great reduction in hull drag, and a further corresponding increase in speed.

Lori Singer (born November 6, 1957) is an American actress and cellist. She is perhaps best known for her role as Ariel Moore, the female lead in the 1984 feature film Footloose, and as Julie Miller in the television series Fame.

Singer was born in Corpus Christi, Texas. She grew up in a musical family: her father, Jacques Singer, was a famous conductor and protégé of Leopold Stokowski, and her mother, Leslie, is a concert pianist. Her brother is the actor Marc Singer. As a child, she was often around such luminaries as Leonard Bernstein. Singer is Jewish.

A Juilliard-trained cellist, she was a student of Leonard Rose. Singer made her debut as soloist at age thirteen with the Oregon Symphony. Singer has performed in public on such stages as the Royal Albert Hall and Carnegie Hall. She plays the cello in Short Cuts, Fame, and also in Sarabande, a 1997 short film by Atom Egoyan that is part of the Inspired by Bach series. Singer performed as soloist at Carnegie Hall in January 2008, premiering a hymn written by Karl Jenkins in memory of Martin Luther King, Jr.

Harry Julius Larsen (September 4, 1915 – August 12, 1974) was a Danish rower who competed in the 1936 Summer Olympics.

In 1936 he won the silver medal with his partner Peter Olsen in the coxless pairs competition.