Answer by Danavir Goswami
Here is an appropriate verse from Sri Garga samhita 1.5.22:
nägendra-kanyakäù çeñaà
bhejur bhaktyä varecchayä
saìkarñaëasya räsärthaà
bhaviñyanti vraje ca täù
näga—of snakes; indra—of the king; kanyakäù—the daughters; çeñam—
Lord Çeña; bhejuù—worshiped; bhaktyä—with devotion; vara—a husband;
icchayä—with the desire; saìkarñaëasya—of Lord Saìkarñaëa;
räsa—of the räsa dance; artham—for the purpose; bhaviñyanti—will be;
vraje—in Vraja; ca—also; täù—they.
TRANSLATION
Snake princesses that, desiring Him as their husband, worshiped Lord Çeña,
will take birth in Vraja (to attain) Lord Balaräma’s räsa dance.
PURPORT (Ours)
The Srimad-Bhagavatam describes that many nagas or multi-hooded snakes reside in the lower planetary systems such as Patala. The master nagas such as Vasuki, Sankha and Kulika all give respect to the greatest and most beautiful snake incarnation of Godhead, Sesa, who has 1,000 hoods. The daughter-princesses of the naga kings worshipped Lord Sesa and desired to have Him as their lover. Since Lord Balarama expands as Sesa-naga, it was fitting for the princesses to become gopis in Vrndavana and enjoy dancing with Him. Thus, Lord Balarama’s rasa-lila dance features distinct gopis, who had been praying to become His consorts for a long time.