* Q1 profit forecast 15-17 cents/shr vs. est. 17 cents
* COO Nina Richardson resigns
* Holiday quarter revenue rose 75 pct
* Shares fall nearly 18 pct after the bell (Adds forecast, COO resignation, updates share price)
By Subrat Patnaik
Feb 5 (Reuters) - Action camera maker GoPro Inc said its chief operating officer was resigning and forecast first-quarter profit slightly below Wall Street's expectations, sending its shares down nearly 18 percent after the bell.
Nina Richardson will leave the company effective Feb. 27, GoPro said in a regulatory filing, without giving a reason for her departure. She has been chief operating officer since February 2013, GoPro says on its website.
The company also said it expects a profit of 15 to 17 cents per share on sales of $330-$340 million for the first quarter of 2015.
Analysts were expecting a profit of 17 cents per share on revenue of $324.7 million, according to Thomson Reuters I/B/E/S.
GoPro dominates the action camera market with a 94 percent share - closest rival Sony Corp has 3 percent - and videos taken using its cameras mounted on helmets, surfboards, bikes and dog harnesses have made a big splash on the Internet.
The company shipped 2.4 million cameras in the fourth quarter ended Dec. 31, helping boost revenue by 75.4 percent.
GoPro's shares gained about 14 percent in extended trading after it reported results on Thursday, before their dramatic reversal of course.
San Mateo, California-based GoPro's resounding success to date has prompted several companies, including Garmin Ltd , Panasonic Corp and Polaroid, to launch their own action cameras.
The market has also attracted the attention of Apple Inc , which in January was granted a patent for a wearable camera that could be mounted on bike helmets and scuba masks.
GoPro launched the latest version of its flagship Hero camera and a cheaper entry-level camera in September, targeting holiday season shoppers.
GoPro sold an average of 1,000 units per hour in the fourth quarter, founder and Chief Executive Nicholas Woodman said.
The company reported fourth-quarter net income attributable to GoPro shareholders of $122.1 million, or 83 cents per share, compared with $33.3 million, or 33 cents per share, a year earlier.
Revenue rose to $633.9 million from $361.5 million.
Analysts were expecting a profit of 70 cents per share on revenue of $580.3 million, according to Thomson Reuters I/B/E/S.
Up to Thursday's close of $54.37, GoPro's stock had more than doubled since its market debut in June. (Editing by Saumyadeb Chakrabarty and Robin Paxton)