In Lena's Bath, the modern dance ninjas in Winston-Salem's alban elved dance company just add water (in a small black pool on stage) to surgically precise choreography and daring balance moves. The result: a bravura, semi-slapstick work that explores the stranger possibilities of a couple trying to administer a bath. If you caught the sneak preview last summer at American Dance Festival, wait 'til you see what it looks like now. The flow's in Duke's Sheafer Theater Thursday, Feb. 17 through Saturday, Feb. 19 at 8 p.m. with a 3 p.m. matinee Sunday, Feb. 20. Discount tickets for dance students bring $20 general seats down to $15 on Thursday and Friday; Duke students and staff get in all shows for $5. Call 684-4444 for the discount rate and for reservations.