30's swimming in colour (with a little bit of late 20's thrown in for good measure)

1930's bathing suit at the Metropolitan Museum New York

via Velvet & Linen blog

1928 bathing suit via fuzzylizzie.com/swimsuits -
- on this website you will also find a great article on vintage swimwear

1929 bathing suit via fuzzylizzie.com/swimsuits - I love this one!!!

1932 wool swimsuit with adjustable ties via  fuzzylizzie.com/swimsuits

1936 swimsuit made of a lastex/wool mix for a better fit via  fuzzylizzie.com/swimsuits

Jantzen suit

1936 bathing suits at the Metropolitan Museum NY

 
red wool bathing suit by B. Altman & Co., 1932. via yeoldefashion tumblr

1933 bathing suit, via retroknittingcompany

via Sonne nach Wunsch flickr


And below, a pattern you can actually knit via A Stitch in Time vol 1.
This one comes with the perfect body too :)

1920's beach babe

Santa Monica 1920's via losangelespast tumblr

1920's bathing beauty via ozfan22.flickr.com

 

Marie Prevost  for Photoplay, 1921, via the loudestvoice.tumblr

Viola Dana in The Beauty Prize, 1924, via valentinovamp.tumblr

...seen that checkered bathing suit before?...

a fresh Joan Crawford in the 1920's via bogarted.tumblr

1928 beachwear, via maudelynn tumblr

Carole Lombard, 1928, via maudelynn tumblr

moving slightly into the next decade, Miss Florida 1930, Margaret Ekdahl, via historyful.tumblr

the very gorgeous Thelma Parr, photographed by George Cannons

 

1930's bathing, via drama of exile tumblr

and the badest beach bum of them all, via tobycreek etsy