The Batman (1966) episode "Surf's Up! Joker's Under!" features Batgirl wearing a sexy one-piece bathing suit... and Batman and the Joker wearing swim trunks over their regular suits for a surfing contest.
It can be argued that Baywatch was nothing but an endless series of beach episodes. That is largely the source of its high ratings.
The Brady Bunch Season 4 opener in Hawaii is both textbook and an extended beach episode. Particularly with the scenes involving Greg surfing (and having his surfing accident), Greg later going girl watching and later the episode-clinching luau. Not much plot, as Barry Williams later pointed out in his autobiography "Growing Up Brady," although it was a great way to get guest star Vincent Price involved.
An episode from later in Season 4, "Greg's Triangle," features Greg's babelicious (but conniving) girlfriend Jennifer Nichols (Tannis G. Montgomery) in a 1972-era bikini, in a scene set at the beach.
One episode of The Brittas Empire features Brittas whisking the staff off to their regular holiday at the fictional seaside town of Burbage-on-Sea, where Gavin takes Colin's potato-powered lilo for a ride and gets captured by Ruthless Modern Pirates as a result.
The Buffy the Vampire Slayer 5th season opener starts out as a beach episode, but mere minutes in, Willow ignites a cookout fire with a spell that causes an elemental imbalance and a sudden storm. End of beach time. Of course, it's also possible that the storm was due to Dracula plonking his castle down outside of town.
Burn Notice is set in Miami FL specifically for the purpose of setting up meets either on Miami Beach or a swimming pool or hot tub, with tons of extremely attractive women in teeny-weeny bikinis parading past the camera before we focus on whoever Michael is meeting at the moment. This qualifies because Michael could as easily meet at the park or a deserted alley, but no, it has to be somewhere where swimwear is required. Partially justified because (as Michael says in a voice-over) "The beach and pools are great places to meet if you don't want to have to search people for weapons or microphones". He has never figured a good way to hide a gun in a swimsuit and even hiding a listening device (somehow) tends to get skewed when meetings are held in hot tubs.
Charmed: Season 6 premieres at a beach party where Phoebe is there to interview the DJ for her magazine. Features Smash Mouth performing and Alyssa Milano in a bikini.
El Chavo del ocho also had a two-parter in Acapulco, starting when La Chilindrina buys a ticket for a raffle to get a full-paid vacation for herself and her dad. Everybody else in the vecindad decides to follow suit and coincidentally, they all end up staying at the same hotel. Like the above, Hilarity Ensues.
Chuck quite gleefully embraced its use of Fanservice with several episodes a season that put characters in bathing suits (or less, with one episode set partially at a nudist retreat). Especially Sarah, though Ellie and Devon at times got in on the action. Hilariously, one episode in season 5 involved Casey trying to balk at an on-again/off-again lover/rival trying to get him into a banana hammock, with Sarah immediately Lampshading how many skimpy outfits she had been required to wear over the course of the series.
The show tried hard to avert the filler aspect: Sean leaves in a Beach Episode.
There's also another one that introduces Paige's brother Dylan. And Spinner has to choose between Jay's friendship and Darcy's love in yet another.
All together it's not quite Once a Season but rather a lot happens at the beach considering the school year and beach season only overlap by a month or so at either end in the Great Lakes region...
Most of "Don't Look Back" takes place at the beach.
Doctor Who: The pre-1989 show had "Planet of Fire", the opening portion of which is set at broadcast date on a beach on Lanzarote, one of the Canary Islands, leading to new companion Peri being introduced in a bikini with much Male Gaze and outgoing companion Turlough first appearing in some very small swimming trunks. (With Male Gaze of a different nature.)
The short-lived Falcon Beach was pretty much nothing but this. How did this show not survive? Oh, right, Screwed by the Network, which gave it a horrible time slot. And no, this wasn't FOX's fault. Actually, FOX would be a logical place for this show...
In the third season finale "The One At The Beach" the gang arrive at the beach house but it's pouring rain and everyone has to stay inside. The house is filled with sand due to flood damage, which at least means they're able to bury Joey in a mermaid-shaped pile of sand. Played straight by the fourth season premiere, "The One With The Jellyfish" where the weather clears up and Monica, Chandler and Joey are able to go out...but then Monica gets stung by a jellyfish and Chandler has to pee on her leg to kill the pain.
Happens again in season 9's "The One in Barbados" because they arrive there during hurricane season. The storm ends briefly but the gang can't go out because they have to attend a presentation Ross is giving. By the time it ends the hurricane has resumed, forcing them to stay inside again.
Gavin & Stacey had pretty much every main character headed over to the beach in Series 3 Episode 5. Bearing in mind, though, that Doris and Bryn were among those getting into their swimsuits, fanservice wasn't really the word for a lot of it. It did move the plot along considerably, though.
The third season-opener for Growing Pains, titled "Aloha," was set in Hawaii.
H₂O: Just Add Water is set in Australia's sunny Gold Coast, and consequently takes advantage of its beach setting in many episodes. The fact that the protagonists are Mermaids certainly helps.
Happy Days had a multi-part beach episode. It involved Fonzie and a shark.
The Hercules: The Legendary Journeys episode "The Apple" featured our heroes at a beach. It's heavier in plot than most beach episodes, but the fangirls get to see Hercules and Iolaus almost naked. And Iolaus invents surfing! The series itself is already known for quite a bit of regular fanservice every episode as well.
The Impractical Jokers film an episode in Miami, and one of their games is on the beach.
It's Always Sunny in Philadelphia has its Jersey Shore episode where the gang goes to the beach for a relaxing vacation. Dennis and Dee wish to show Charlie how great it is and rekindle their fond childhood memories of vacationing there while Frank and Mac are unenthusiastic. Dennis and Dee wind up having a terrible time, while the other three find it enjoyable.
There was also another episode that initially seemed to be this but ended up being about being stuck in a traffic jam. Peg, Kelly and Bud even occasionally walked their way back and forth between their car and their house.
The Monkees. As they live in a shabby house on the beach, scenes from many episodes take place on the beach. Most notable is the episode "Monkees at the Movies".
Murdoch Mysteries: "Loch Ness Murdoch" starts with Inspector Brackenreid at the beach during a heatwave, with other characters joining him later.
My Rosy Life: In episode 22 the whole family goes to Jeju Island for a beach vacation. Sung-moon, who was cheating on his wife Soon-yi and behaved just terribly to her, has been The Atoner after finding out she is dying of cancer, and takes her to the beach to spend some happy time with the time she has left.
Neighbours episode #417, listed on an Iconic Episodes DVD set as "Charlene on Beach in Bikini." To be fair, it was part of a "Scott and Charlene" disc.
Noah's Arc: The last episode of the second season, during the Pride beach party. Though the first half of the episode plays the trope straight (purely fanservice and relatively relaxed), the last half cranks the drama up a pinch.
The Office has an episode where they went to the beach. Or rather, the side of a lake. Subverted in that hopes of beachy fun and Pam in a two-piece were dashed as Michael used it as an excuse for a Survivor style event to pick his successor, and the episode features some of the best character development to date.
Subverted in Person of Interest season 2 when Reese searches for a serial killer on Owen Island. He points out that he's going to the beach, except its hurricane season.
Pizza has a Season 5 episode, Beach Pizza Parts 1 & 2. The day explodes into mayhem as pizza deliveries go wrong and Habib and Rocky accidentally start a riot with lifesavers. The media then interview Pauly and he is taken out of context and blamed as the instigator of the Cronulla Beach riot. So it is against the Lebs vs. Aussies.
Commonly seen in thefirstfewseasons of Power Rangers, though it got both the males and females into fanservice outfits. Which explains one of the reasons why older fans of either sex may have loved the show so much. While these episodes were almost always filler as usual with the trope, it must be noted that 85% of any given early season of PR is filler anyways. You also see a lot of the beach in Ninja Storm, what with it being New Zealand and everything.
S Club 7's TV series had its first two seasons set in Miami and Los Angeles respectively, requiring beach settings in many episodes. However, one specific Miami 7 episode centered around a volleyball game and therefore more time on the beach than normal. An episode of LA 7 also had Hannah and Tina trying to learn how to surf to impress a pair of Surfer Dudes. One of the band's music videos played this straight too (see 'Music' below).
Parodied in Season 6 when her aunts cast a spell as Sabrina and friends go on their spring break - and they end up living one of the 60s beach party movies having "Good Clean Fun". Frankie Avalon stars As Himself.
Earlier in the Season 3 finale, the Spellmans go to a family reunion in Hawaii. There is however the resolution of Sabrina's family secret - that she has an Evil Twin - but they do take advantage of this to put the females into flattering beach wear.
One of the TV movie spin-offs was Sabrina Down Under - about Sabrina visiting Australia and meeting the local merpeople.
Six episodes of Saved by the Bell's third season featured the main cast working in a beach resort over the summer.
Scrubs has The Janitor's and Lady's Wedding set in the Bahamas.
South of Nowhere's "Girl's Guide to Dating" had Spencer and Ashley ditching school for the beach, and end up missing a lock-down. Doubles as a Coming-Out Story.
Star Trek: Deep Space Nine: The episode "Let He Who Is Without Sin..." has Worf and Dax take a vacation on Risa, a Pleasure Planet featuring beaches that look suspiciously like Malibu. Of course, Worf is in no mood for fun in the sand and gets into trouble with some Well Intentioned Extremists.
Step by Step: The Foster-Lambert family travels to Hawaii for the two-parter "Aloha."
Actor Jensen Ackles likes to joke that he's been trying to pitch the "Demon Surfer" episode of Supernatural so they can film in Hawaii and have a Beach Episode. Strangely, this tends to happen in a lot of Supernatural fanfics.
Even The Thick of It had a beach episode: the party conference episode in series three, for which the action moved to a hotel in Eastbourne. Being The Thick Of It, this was just as unglamorous as all the other episodes. No swimsuits were seen: the closest we got was Terri in her cagoule on a windswept beach.
The Time In Between: One episode during the Morocco arc features Rosalinda, Sira, Felix, and Marcus taking an impromptu trip to the beach to get away from their problems in Tetuoan.
Tropical Heat, like Baywatch mentioned above, was basically a beach episode every time, being set in Miami.
The Vampire Diaries had "Welcome to Paradise", where Elena arranges a party at a local lake.
Victorious has the cast go to a beach, but end up getting trapped in an RV.
Wonder Woman: "Skateboard Wiz" is set on a beach complete with Diana Prince sunbathing before being accosted by mooks. She reminds them forcefully that she is a trained amazon before transforming into Wonder Woman and then really working them over.
