Sea Ghosts, a new dance by the Ellen Sinopoli Dance Company, will be performed on March 24 at the Ulster Performing Arts Center (UPAC) as part of the 29th annual Festival of Dance. An otherworldly, subterranean realm is immediately established by the dramatic backdrop, a 15-by-20-foot banner reproducing a colorful, gestural painting by Woodstock-based artist Calvin Grimm. Dramatically blown up from the original artwork, the image is a touchstone for the tentaclelike movements of the dancers, who seem to float and writhe in an aquatic world, whose wavelike rhythms and underwater resonances are further conjured up by the eerie sound piece written by Chicago composer William Harper. The set piece is a first for Grimm, who, after attending a Sinopoli Dance Company piece at Kaatsbaan, the dance center in Tivoli, approached Ellen Sinopoli about a possible collaboration.