Much like the Navy, women's sports are really, really gay.
The Lesbian Jock, as her name would suggest, loves sports and also loves the ladies. Usually, this trope either takes the form of lesbian characters playing sports, or other people assuming (correctly or incorrectly) that a female character is a lesbian because she enjoys sports. There seems to be a sliding scale of which sports are acceptable for girls without questioning their femininity and which are not. Performance-based sports like gymnastics, figure skating, diving, and cheerleading are all "okay"; most competitive sports like softball, volleyball, track, soccer, tennis, and basketball are 50/50; but "masculine" sports like wrestling, American football, rugby and, strangely enough, golf are almost a sure bet. One common subtrope is the Butch Lesbian P.E. teacher.
Her rough Spear Counterpart could be considered the Gym Bunny. However, the lesbian jock is usually into sports because she's a tomboy while the Gym Bunny is usually into physical fitness because he's a narcissist. The counterpart of this trope is Lipstick Lesbian.
From this standpoint, the Spear Counterpart would be Performance Artist, where certain performance arts are 'reserved' for women and that any man who choose to partake in them are automatically more 'feminine' (and thus in turn inclined to homosexuality) than those who don't. The same logical fallacy applies.
A variant, with many of the same stereotypes, is the Lesbian Cop.
Subverted in Nyan Koi!. Nagi Ichinose is the captain of the school track team, a Bifauxnen who induces Viewer Gender Confusion and plays the part of a Chivalrous Pervert around the other girls. However, she comes to develop a crush on the male main character... While still ogling every other girl in sight.
According to Word of God, Betty Buckley played Miss Collins as this in the 1976 version of Carrie. However, instead of being a Butch Lesbian like many versions of this trope, she has a very feminine appearance, and the bulk of her interaction with Carrie is complimenting her looks and giving her beauty tips. She also mentions having taken the captain of the basketball team to her own prom, although this doesn't rule out her being closeted what with her prom taking place in the 60's.
In the short film Size 'Em Up, the teenage soccer player Sam (played by Lindsay Felton) is heavily implied to be a lesbian.
In Stardom, main character Tina Menzhal (Jessica Pare) mentions that she had been with girls before. Her friend is surprised, but Tina says that it's not really unusual because she played softball in school, and uses the phrase "dykes on spikes" to describe the phenomenon.
In Girls FC, it isn't stated outright, but it's pretty heavily implied near the end of book 8, when Tabinda asks her coach Hannah if she ever gets afraid of anything. Hannah replies that she wanted to tell her parents something about herself, but was afraid to. When she finally did, they told her, "Oh, we've known that for ages".
Live Action TV
Dana Fairbanks from The L Word is a professional tennis player, and season four introduces the character Papi, who plays basketball and admits that she likes to go to games to pick up girls.
In Boston Public, there was a short controversy inside the school when the rumour got out that the girls PE teacher was lesbian, and had choreographed the cheerleading routine for her personal entertainment (and, admittedly, the entertainment of any male viewers.)
The Golden Girls had several references to lesbians and tennis. Rose also mentioned a "very confused female PE teacher" being a customer at her kissing booth.
In a flashback on Friends, Ross gushes that his girlfriend Carol, later his lesbian ex-wife, plays on both the lacrosse team and the golf team.
Wendy: What exactly are you saying? Dave: Look... well, we know that all female cricketers are lesbians. (Crowd goes wild). Corinne:Every single one of them, Dave. The whole lot of them. You know, I touched a cricket bat once and I had lesbianitis for three weeks. The whole lot of them. Dave: Uh... well... could we just move on?
In an episode of The West Wing C.J. has to contend with rumours that she's gay. The "evidence": She played basketball in high school. Yes. So what if she's incredibly tall?
Coach Beiste of Glee invoked this, explaining specifically that she is NOT. Doesn't help she looks like a Butch Lesbian.
Law & Order: Criminal Intent: There are several hints that an African-American female lacrosse player has a crush on her friend and later the detectives ask her father which would be worse for him, her being a lesbian or a murderer (he doesn't respond and she's not a murderer. A little overzealous in defending her friend's honor, but not a murderer).
Harry's Law: An athletic high school student is Driven to Suicide after another student, a popular blogger, gets the entire school to harass her out of the closet. The blogger's justification is that A) there are gay students who are comfortably out and B) she just didn't think about her victim's feelings or that her family/friends outside school/church might not be as accepting as the school it works, she's found not guilty of murder.
Jane of Degrassi was accused of being a budding lesbian because she was changing in the girls' locker room for football.
Emily on Pretty Little Liars definitely fits the lesbian part. Whether or not being a swimmer counts as being a jock is debatable, but her girlfriend Maya has called her such on occasion.
There is also Paige, who is a lesbian that is a swimmer and a field hockey player. She even has a penalty named after her. She doesn't actually qualify as a Butch Lesbian though.
Lisa from Venus Envy. Later on, it's revealed that the rest of the girls' soccer team is gay as well, except for one girl who nervously admits that she might be straight.
El Goonish Shive did a joke about this as well, when Justin heavily intimated that watching women's volleyball was inherently homosexual.
Though this may have been a lot less "jock" and a lot more "bouncy boobs." Obviously, there are people who watch women's volleyball for other reasons, but...
Subverted in Red String. Maya gives off all the right clues: awesome athlete, tall, tan, has a close friendship with both Fuuko and Karen. Then it turns out (after a scandal, a friendship split, and a lot of soul-searching) that feminine and frilly Fuuko is gay, but sporty jock Maya is straight.
Reiko Ishida, of Survival of the Fittest, is a rare example of one of these that does ice skating. Despite the fact that, as noted above, it tends to be seen as "girly", she is masculine enough (and, well, the obvious) to count as being played straight.
During the episode where Homer became a gay-marriage minister, Marge's sister's lesbian fiance was a pro-golfer. Then it turns out that "she" is really a "he".
When Lisa is tempted by a full-ride scholarship to any one of the "Seven Sisters" womens' colleges, she has a dream sequence where an avatar of each of them speaks to her. Smith College is represented by a Butch Lesbian in a Lacrosse uniform that tells her "Come to Smith... and experiment."
This was used as a throwaway gag on The Critic - Jay had a Dream Sequence where he imagined the first girl who kissed him - who later became a lesbian on the women's golf tour.
In an episode of Family Guy, Meg's gym teacher instructed her students to get in the shower and bounce around, like it was a normal thing. She is officially confirmed to be lesbian in a later episode, where she is seen at the sperm bank with her partner.