Translation guide
In Japanese, the most common word for 'bathing suit' is 水着 (mizugi). There are also specific terms for different styles, such as school swimsuits or bikinis.
水着
bathing suit
The speaker wants to refer to a bathing suit or swimsuit in general, for any gender or age.
The standard, all-purpose word for swimsuit or bathing suit. Used for men's, women's, and children's swimwear.
新しい水着を買った。
I bought a new bathing suit.
水着に着替える。
I'll change into my swimsuit.
Literally 'sea-water wear'. A slightly more formal or old-fashioned term for a swimsuit, often used for women's swimwear. Less common in everyday speech.
海水着の展示会に行った。
I went to a swimsuit exhibition.
The speaker wants to refer to the specific type of swimsuit worn in Japanese schools, typically a one-piece with a name tag.
Refers to the standard swimsuit used in Japanese schools, usually a dark blue one-piece with a name tag area. Commonly used by students.
スクール水着に名前を書く。
Write your name on your school swimsuit.
The speaker specifically means a two-piece bikini.
The loanword for bikini. Used exactly as in English.
ビキニを着てビーチに行く。
Wear a bikini and go to the beach.
The speaker wants to refer to tight men's swimwear, like Speedos.
Literally 'competitive swimming swimsuit'. Refers to racing swimwear, often tight briefs or jammers. Can be used for men's swim briefs in general.
彼は競泳水着で泳いでいる。
He is swimming in racing swimwear.
Loanword for swim briefs. Not as common as 競泳水着, but understood.
スイムブリーフを履く。
Wear swim briefs.
The speaker means loose-fitting men's swimwear, like board shorts.
Loanword for surf pants or board shorts. Common term for longer, loose swim trunks.
サーフパンツをはいて海に入る。
Go into the ocean wearing board shorts.
Literally 'swimming pants'. A general term for men's swim trunks or shorts.
水泳パンツを忘れた。
I forgot my swim trunks.
In most everyday situations, 水着 (mizugi) is sufficient for any type of swimwear. You don't need to specify the style unless it's important.
海水着 (kaisuigi) is an older term and can sound dated or formal. Stick with 水着 in conversation.