  Banks

Banks as a girls' name was brought into the lexicon by actress Hilary Duff and musician Matthew Koma, who chose it for their daughter, Banks Violet. As both a surname and a word name, Banks refers to financial establishments as well as river banks.

Banks

Like River and Lake, a cool, refreshing modern water-related choice. 

One of the most usable of the pleasant, newly adopted nature/water names (like Lake and Ocean), especially in middle position. 
 There was a character named Bay Kennish on the show Switched at Birth; conservative political commentator Bay Buchanan was born Angela Marie.
 Other associations with bay are the bay laurel tree, prized since ancient times for its medicinal and culinary (bay leaves!) properties, and the reddish-brown color usually applied to horses.

A slow and sultry southern choice that's definitely cool for babies of either gender. 

Bayou

Intriguing, when seen as a <a href="https://nameberry.com/list/10/water-baby-names">water name</a> a la River and Ocean, but too close to cultural appropriate if used as a reference to the Creek tribe of Native Americans. Another downside is its resemblance to creak, as in creaky bones or floorboards, and to unappealing words like creep and creak.

Creek

Delta is an unusual vintage option with a lazy-day-down-by-the-river feel. Delta is the fourth letter of the Greek alphabet and also the geographical name given to an island formed at the mouth of a river. 

 Australian singer Delta Goodrem is a notable modern bearer.

Delta

Iris has so much going for it. It's a fashionable flower name. It's a mythological name, from the Greek goddess of the rainbow. And it's a classic name, always ranking in the girls' Top 1000 but now at its highest point ever.
 
Iris is directly derived from the Greek word iris, meaning "rainbow." In Greek mythology, rainbow goddess Iris was a messenger for Zeus and Hera who rode the rainbow as a multicolored bridge from heaven to earth. 
 The botanical iris also carries evocative symbols. In ancient times, the Iris was considered a symbol of power and majesty, the three petal segments representing faith, wisdom and valor. This image led to the naming of the colored part of the eye.
In the contemporary world, Iris has amazing international versatility, ranking highly throughout the English-speaking world as well as in a diverse range of countries from Spain to Slovenia, France to Sweden.
 Part of Iris's rise is due to its celebrity power: Jude Law and Sadie Frost, Judd Apatow and Leslie Mann, and Renee O'Connor all chose Iris for their daughters.
 A notable modern bearer was the prolific British novelist Iris Murdoch. Frequently seen on screen, characters called Iris have been played by Jodie Foster, Jane Fonda and Kate Winslet, and Iris Chase is the narrator in the Margaret Atwood novel The Blind Assassin.

Iris

Kai is an internationally flexible name with many possible origins and meanings, growing in popularity in the US and a diverse range of European countries.
 
In the US, the name Kai is most commonly referred to as being of Hawaiian derivation, meaning "sea." In Europe, Kai is largely considered to have Frisian origin as a diminutive of the name Kaimbe, meaning "warrior", or as a short form of Gerard "brave spear". 
 
Kai is also found as an independent name in African, Chinese, Turkish and Native American cultures. Kai is a strong, evocative multi-cultural name that packs a lot of power in its single syllable. 
 
Famous as the name of the boy enchanted by the fairy-tale Snow Queen, Kai was chosen for her son by actress Jennifer Connelly and as a middle name for son Samuel by Naomi Watts and Liev Schreiber. 
 
Kai is popular with Berries as both a first and middle name choice. Perhaps because of its international familiarity, Kai is popular in video games. Its most prominent namesake is Danish-born jazz trombonist Kai Winding.
 
Kai ranks in the US Top 1000 for girls, but is used more than 90 percent of the time for boys. Donald Trump, Jr. has a daughter named Kai Madison and Gigi Hadid and Zayn Malik named their daughter Khai in 2020.

This appealing multi-cultural name, pronounced KYE, is beginning to be used for girls as well as boys. Among its many derivations and meanings: "sea" in Hawaiian, "forgiveness" in Japanese, "willow tree" in Navajo, "food" in Maori, and "earth" in Scandinavian. For girls, it debuted on the US Top 1000 in 2010.

Evocative modern unisex choice brought into the spotlight by actress Lake Bell. 

Lake

This body of water runs deep; the best of a group of new possibilities that includes Bay, Ocean, River, and the more established Brook. It has received attention via the actress Lake Bell. Lake would make a particularly cool and refreshing middle name, as Gisele Bundchen and Tom Brady did for daughter Vivian.
 Lake is also a fairly common surname, represented by 1940's blonde femme fatale Veronica (born Constance Ockelman), actress/talk show host Ricki and Emerson, Lake & Palmer bassist Greg.

Nimue

Oasis

Nature names like Ocean and River are flowing back into favor, especially with nature lovers and green-oriented parents. 
 Forest Whitaker, an inspired child namer (his other kids are called Sonnet and True), has a son named Ocean Alexander.
 Variations include Oceanus, the name of the child who was born during the voyage of the Mayflower, and Oceane, a wildly popular girls' name in France.

Ocean

Ocean is a nature name that comes right out and states its meaning and association. Full of power and depth, Ocean is one of the fastest-rising baby names for both girls and boys, making the US Top 1000 for both genders in 2021. Oceane, the version that's trendy in France, was used for only 11 baby girls in the US in the same year.

Ocean-lovers who want to be less obvious can choose such subtler <a href="https://nameberry.com/list/641/names-that-mean-ocean">names that mean ocean</a> as Jennifer or Marissa, but coming right out and using Ocean is a perfectly valid way to go.

Oceane (oh-see-EN) has been one of the chicest names in France for several years, ranking in the French Top 50. This is a sophisticated name that could easily cross the ocean, and is much more stylish than the English Ocean or Oceana.
 This group of names all relate to the ancient Greek Oceanus, god of the open sea and the oldest Titan, son of Uranos and Gaia. If you're looking for uncommon <a href="https://nameberry.com/list/641/names-that-mean-ocean">names that mean ocean</a>, this is one to consider.

Oceane

Wildly popular name in France that could easily cross the Atlantic. 

Océane

Mostly feminine, though "Office" star Rainn Wilson gives it a slight masculine twist.  You might also use this as a short form of Raines.

Rain

Among a small shower of rain-related names, this pure version can have a cool, refreshing image. 
 Richard Pryor named his now-grown daughter Rain, and Rain is also one of the nature-named Phoenix family siblings. More recently, 24 actress Marisol Nichols named her daughter Rain India.
 Rain also makes a nice nature middle name--Brooke Burke called her daughter Heaven Rain.
 If you want to embellish this simply spelling (and alter the meaning), you might also consider Raine, Raina, Rainn, Rayne, Reine or Reign, the middle name of Willow Smith. Or you could take the Holly Madison route all the way to Rainbow.

Colorful, yes, but also probably among the hippiest of hippie names. Holly Madison recently chose it for her little girl.

Rainbow

Rainn

Modern surfer boy. Just don't call him Reefer. 

Reef

Rio is a reductive ranchero place-name with an attractive Tex-Mex lilt. No Doubt's Tom Dumont has a son named Rio Atticus. 
 Also a South American place name, and associated with the Rio Grande, it's been used as a swaggering cowboy name in films spanning from a William S. Hart character in 1915 to Marlon Brando's in One-Eyed Jacks. It is occasionally used for a girl, as in the catchy Duran Duran song.

Rio is one of Japan's most popular girls names, constantly sitting in that country's Top 10. Of course, Rio may also stem from the Portuguese and Spanish word for river, and the Brazilian city Rio de Janeiro. A truly international name for a cosmopolitan baby!

River shares the tranquil feeling of all the water names, and seems to have pretty much escaped its past strong association with River Phoenix and his unfortunate fate. Actor Joaquin Phoenix named his son with actress Rooney Mara after his brother River.

River's popularity is rising for boy genders, but it's still predominantly given to baby boys. Last year nearly 3500 boys were named River vs. about 1900 baby girls.

Keri Russell and the Taylor Hansons both have sons named River, Natasha Henstridge used it as the middle name of her boy Tristan, and Jason Schwartzman pluralized it for daughter Marlowe Rivers.

River

Most of the notable Rivers have been male, but this nature name certainly flows as well for a girl. The name River is still rising for both genders, with about 3500 baby boys receiving the name last year vs. 1900 baby girls.

Kelly Clarkson's choice of River for her newborn daughter further raised the profile of the <a href="https://nameberry.com/girls-names">name for girls</a>. Baseball great Derek Jeter and Hannah Davis used the same name as Clarkson for their daughter born in 2021, River Rose.

With River and Ocean becoming mainstream, why not consider Sea?

A natural phenomenon that makes a stylish baby name. Teen Mom's Kailyn Lowry used it for her daughter, twin to Verse.

Valley

vix's list "unique water related names" of 31 great name ideas:   Banks - Valley!