“Tarzan” is a fictional character in the books by Edgar Rice Burroughs (1875-1950). “You look like Tarzan but you swim like Jane” was cited in 1965 and said of a man who can’t swim well. Hippies “have haircuts like Tarzan, act like Jane and smell like Cheetah” was said by California Governor Ronald Reagan.
 
In sports (especially football), a player who “looks like Tarzan but plays like Jane” is someone who is great physically, but who can’t play the game. “The Browns had a succinct report on one collegiate hopeful ‘Built like Tarzan, plays like Jane’” was cited in print in 1971. “Looks like Tarzan plays like Jane” was cited in 1975.
 
   
Wikipedia: Tarzan
Tarzan (”...the Apeman”) is a fictional character, an archetypal feral child raised in the African jungles by the Mangani “great apes”; he later experiences civilization only to largely reject it and return to the wild as a heroic adventurer. Created by Edgar Rice Burroughs, Tarzan first appeared in the novel Tarzan of the Apes (magazine publication 1912, book publication 1914), and then in twenty-five sequels, three authorized books by other authors, and innumerable works in other media, authorized and not.
 
9 July 1965, Evening World-Herald (Omaha, NE)< "How to Swim Without Really Swimming" by Bill Vaughan, pg. 18, col. 4:

“Hey, Weissmuller, you look like Tarzan but you swim like Jane.”
 
15 October 1967, Sunday World-Herald (Omaha, NE),  “Washington Scrapbook” by Walter Trohan, pg. 23-A, col. 4:
Washington—Gov. Ronald Reagan of California, raising money for the Republican Party in Columbia, S. C., told his audience that hippie pickets protesting against just about everything “have haircuts like Tarzan, act like Jane and smell like Cheetah.”
(The authorship of this line has been credited to Pat Buttram.—ed.)
     
30 January 1971, Plain Dealer (Cleveland, OH), “Notes off the Cuff” by Buck Heaton, pg. 1-C, col. 6:
The Browns had a succinct report on one collegiate hopeful “Built like Tarzan, plays like Jane.”
 
6 August 1975, Anderson (IN) Daily Bulletin “Football relaxes Paul Brown” by Rick Bozich, pg. 13, col. 5:
“It’s an old story,” he says, smiling. “Looks like Tarzan plays like Jane.”
 
29 August 1977, Morning Advocate (Baton Rouge, LA),  “Vandy: New Era, Or Same Old Song?” by Mike McKenzie, pg. 1-C, col. 4:
Pro scouts say he needs to be more aggressive (one wrote he looks like Tarzan, plays like Jane) so he has determined to “become meaner.”
 
Google Books
The Pro Football Mystique
By Dave Klein
New York, NY: New American Library
1978
Pg. 161:
“Looks like Tarzan but plays like Jane.” Clearly, this player is somewhat short on courage.
   
Sports Illustrated
September 26, 1994
The NFC Central
Jill Lieber
(...)
The word among the Bear players is that Spellman looks like Tarzan but plays like Jane.
 
Fox Sports
Draft lingo is a special language
By Adam Caplan
UPDATED APR 5, 2011 1:48 PM ET
(...)
“Looks like Tarzan, plays like Jane”
This could be my favorite all-time scouting term.
 
Don’t ever let a player hear you say this about them. If they do, I guarantee you’ll get a shiner.
 
Your first impression was probably correct with this one. I’ve often heard defensive players framed by this term.
 
It refers to a player who looks good in a uniform or physically, but basically can’t play or is very raw.
   
Bleacher Report
7 NFL Players Who Look Like Tarzan, but Play Like Jane
By Alessandro Miglio , Featured Columnist Dec 28, 2012
 
Twitter
Cody Bartlett
‏@cody_barto
@ProFootballTalk you can have him. Looks like Tarzan, plays like Jane.
10:13 PM - 31 Jan 2014