Benzaiten is the only female among the seven lucky gods, and is as closely associated with Buddhism as she is with Shintō. She is regarded as the patron of music, the arts and eloquence, and Chiba associates her with the following occupations: actors, airline hostesses, artists, beauticians, composers, dancers, designers, directors, dramatists, entertainers, gamblers, models, musicians, painters, photographers, sculptors, sword makers, and writers. According to Wikipedia, the author Brian Bocking equates Benzaiten with Ichikishima-hime-no-mikoto, who is the main goddess at one of three main shrines at the Enoshima Jinja.
Benzaiten derives from the Hindu goddess Sarasvati filtered through Chinese translations of Buddhist sutras. Sarasvati herself is the Hindu Goddess of knowledge, music and arts and is said to have been the wife of both Bramah and Vishnu, who, along with Siva, form the holy trinity of Hinduism. The first written mention of Sarasvati is in the Rigveda, one of the four sacred texts of Hinduism and written sometime between 1500 and 1000 BC. The most apposite quote in the Benzaiten context is probably this one from Hymn 41:
<16 Best Mother, best of Rivers, best of Goddesses, Sarasvatī, We are, as ’twere, of no repute and dear Mother, give thou us renown.
17 In thee, Sarasvatī, divine, all generations have their stay.>
Apposite because almost all Benzaiten Jinja in Japan are situated near the sea, rivers or lakes or have their own in-ground lakes. A more tenuous reference to Banzaiten is the following quote from Hymn 61:
7 Yea, this divine Sarasvatī, terrible with her golden path,
Foe-slayer, claims our eulogy.>
he "foe-slayer" can be interpreted as a reference to Sarasvati having kiled Vritra, the three-headed serpent/snake of Hindu mythology. There is, however, no other reference to this, and the standard account has Indra as the slayer of Vritra. In the Benzaiten legend the the three-headed serpent/snake becomes a white snake, which serves as her messenger. A good illustration of this is the Kami-shinmei-tenso Jinja.
Enoshima Jinja 江島神社
Kanagawa-ken, Fujisawa-shi, Enoshima 2-3-8
Zeniarai Benzaiten Ugafuku jinja 銭洗弁財天宇賀福神社
Kanagawa-ken, Kamakura-shi, Sasuke 2-25-16
Kiyomizu Benzaiten Sha 清水弁財天社
Nagano-ken, Saku-shi, Iwamurada
Tenkawa DaiBenzaiten Sha 天河大辯財天社
Nara-ken, Yoshino-gun, Tenkawa-mura Tsubo-no-uchi 107
From India to Japan, Sarasvati to Benzaiten
Sarasvati appears in Chinese translations of two sutras, the Sutra of Golden Light (金光明経, Konkōmyō-kyō), and the Lotus Sutra (妙法蓮華経 Myōhō-rengei-kyō). The former devotes a full chapter (8) to her and is one long, sustained eulogy, Her appearance in the Lotus Sutra is mentioned in virtually every article about Benzaiten on the Internet but I have been unable to trace it. Exactly when she first appeared in Japan is unclear, but it was almost certainly in 6th-8th century AD. Probably reflecting China's Confucian background, much of the Sutra of Golden Light stresses the need for a ruler who governs the country wisely and on her first arrival in Japan it was this aspect, protector of the state and the people, with which Benzaiten was associated. Her name was originally written 辯才天. The first of these three characters means speech, eloquence and the second ability, gift. As she became more naturalised, eventually becoming one of the Seven Lucky Gods her name came to be written 弁財天. The first character of this name, 弁, is a simplified form of 辯 and so represents no real change, but the second character, 財, is quite different from 才 and means fortune or riches, an eminently suitable attribute for a god of luck.
Images of Benzaiten almost always show her playing a biwa, basically a short-necked lute, and Japan's largest freshwater lake, Lake Biwa, is one of the centres of her worship. For more on this, and on Benzaiten Jinja in general, see here.