In the British TV show Dragon's Den, the investors on the panel are usually called Dragons.
Entrepreneurs enter the den to present a business idea, ask for a specified amount of money and offer a percentage of ownership in return. The wealthy businesspeople listening to those pitches are the programme’s Dragons, while the people seeking investment are entrepreneurs or contestants.
The term comes directly from the programme’s title and its international format. Each Dragon has a different business background, so the panel can assess products, finances, intellectual property, marketing and scalability from several perspectives.
“Sharks” is the term used by the related American television franchise Shark Tank, not the standard British name. Although the shows share an investment-pitch premise, their panel names, branding and individual deals are not interchangeable.