'P3 H2O' (Story Code 4399029) by Zack Estrin and Chris Levinson

When the sisters revisit the place where their mother suspiciously drowned, they encounter a watery demon. In order to destroy the creature, Prue must face her greatest fear; in the process, she and her sisters meet a mysterious stranger from their mother's past….

Shannen Doherty (Prue Haillwell), Holly Marie Combs (Piper Halliwell), Alyssa Milano (Phoebe Halliwell), Dorian Gregory (Darryl Morris), Brian Krause (Leo Wyatt), Greg Vaughan (Dan Gordon), Lochlyn Munro (Jack Sheridan), Finola Hughes (Patty Halliwell), Scott Jaeck (Sam Wilder), Pat Crowley (Mrs. Johnson), Emmalee Thompson (Young Prue), Ferrell Barron (Medic), Lucky Luciano (Kid #1)

Directed by John Behring
Produced by Sheryl J. Anderson and Jon Pare
Executive Producers Brad Kern, Constance M. Burge, Aaron Spelling and E. Duke Vincent

TX (US): 9th December 1999

Notes:
*Featuring Prue Halliwell, Piper Halliwell, Phoebe Halliwell and Leo Wyatt