Don’t get your panties in a bunch just because you missed National Underwear Day. Go commando.

DO
Harrison Street Regatta
What: Bring your boat or borrow a kayak for a Hudson River race and mainland BBQ.
Why: Aim to be next best (second boat that crosses the finish line wins).
When: Sat. Registration, 1 p.m.; race, 2 p.m.
Where: Start, Pier 96, at 56th St.; end, Riverside Park S., at 72nd St. More info online at downtownboathouse.org.

EAT
New Jack’s Luxury Oyster Bar
What: The little pearl moves to new tight quarters with a $14-and-under menu for frugal foodies.
Why: Lobster profiteroles, oysters six ways, peekytoe crab tart, spaetzle mac & cheese.
When: Daily, 6-11 p.m.
Where: 101 2nd Ave., at Sixth St. (212-673-0338).

BUY
Interactive Window Shopping
What: Tech-fancy touch screen window lets strollers shop after closing time.
Why: Adds a whole new dimension to dog (or drunk) walking.
When: 24/7 (that’s the beauty of it). Thru Sept. 10.
Where: Ralph Lauren, 888 Madison Ave., at 72th St. (212-434-8000).

SEE
Hermanas
What: Fringe comedy about Jewish-Mexican-Texan sisters, their lovers, and their mother.
Why: They’ll be serving plenty of tequila and Manischewitz.
When: Sat., 4:45 p.m.; Sun., 7:15 p.m.
Where: Classic Stage Company, 136 E. 13th St., b/t Third & Fourth Aves.

HEAR
AUN
What: Electronic phonics from a super-cool Japanese Samurai duo.
Why: Drum up some fun.
When: Sat., 8 p.m.
Where: Knitting Factory, 74 Leonard St., b/t Church St. & Broadway (212-219-3132).