It's part environmental advocacy, part public art, and part wish fulfillment for participants like the event's founder, Alie Vidich, who will, for the second year, undertake an aerial dance suspended from the span of the Strawberry Mansion Bridge.
Vidich said a lot had changed since last year's event - which was allowed to proceed at the last minute after city officials had called the whole thing off. (Though Vidich had worked with several city departments and paid various permit fees, she learned just two days before the event that the Office of Public Safety hadn't been notified. A social-media outcry helped save the day.)
This year's performance is bigger (with a flotilla of 65 dragon boats, kayaks, and canoes for ticketed spectators; dancers on shore, in canoes, on paddleboards, and dangling from the bridge; live music; and art installations). It's also better funded (with an $82,000 grant from the William Penn Foundation) and better planned (Vidich said she has the OK from all relevant city departments this time around).
The goal, though, remains the same: to bring a new constituency to the Schuylkill (the name means "hidden river").
"The idea," Vidich said after a rehearsal last week, "is really to activate the Schuylkill in a way it's not normally activated - to bring people onto the water . . . and use art to change their perspective and to get them interested in being stewards of the river."
Outside the avid rowing and boating communities, most Philadelphians have never been out on the Schuylkill, she noted - and some wouldn't dare.
It even became a factor in recruiting performers.
Amy Lynne Barr, an aerialist who will be performing with Vidich, said, "That's one of the first questions she asked me: How do I feel about swimming in the Schuylkill?"
Those worries aren't totally unfounded: In a previous performance she organized on the river, in 2011, Vidich said "a bunch" of the dancers did get sick. This year, she has been more careful, watching the Water Department's RiverCast for warnings and adjusting accordingly.
But she wants to eradicate some of those fears, and rewind to a happier time for the river.
To that end, musicians Mike Wall and Jon Yerby will set the soundtrack on a pontoon boat alongside the flotilla. They'll perform music on piano, trumpet, and guitar, accompanying various elements of the performance: a community dance group, composed of women 23 to 70, on the edge of Peter's Island; a floating sculptural installation by visual artist Polly Kurasch; and another installation of LED lights on the dragon boat dock.
Jorgensen will also get the opportunity to bring to life the dance she envisioned aboard the canoe last winter: Eight young dancers will perform a rite of summer, enveloped in fabric, by the rowing grandstands on the river's eastern bank.
The supersized performance entails a fairly high degree of difficulty. In addition to 30 dancers, there are 20 technicians involved in lighting, sound, and rigging. Terraquarbor, a Kensington tree-service company, hung the aerial ropes from the bridge, a process that required two days of climbing, knotting, and rappelling.
The flotilla departs from 1233 Martin Luther King Jr. Dr. at 6:15 p.m. Saturday and Sunday, returning between 8:30 and 9. Tickets are $25 and must be purchased in advance at InvisibleRiver.org, though the program is partially visible from places along the eastern shore - the rowing grandstand, Strawberry Mansion Bridge - for free.
Vidich said even the Martin Luther King Drive launch point is meant to make a statement, in support of boaters who want to see a community boathouse on the western bank. "That part of the park has a lot of crime. Three times in the past month my dancers have had things stolen out of their cars," she said. "We need to get people to different parts of the park . . . for the park to change."
Sponsors include the Schuylkill River Development Corp., whose chief executive, Joe Syrnick, said events like this fill an important niche: Anything that brings new visitors to the river helps. Though his group runs kayaks and riverboats, the program has been limited due to funding.
"The lower Schuylkill, where we are, was blocked off by industry for a long time. So it's very important now to redevelop and revitalize that part of the river," he said.
7 p.m. Saturday and Sunday along 2 1/2 miles of the Schuylkill.
Tickets for boat passengers: $25. Boat-landing directions and information at www.invisibleriver.org.