。
She's wearing a cute swimsuit.
Literal
She [topic-は] cute swimsuit [object-を] is-wearing.
水着 (literally 'water-clothes') is the all-purpose word for swimwear — covering bikinis, one-pieces, men's swim trunks, and any garment intended for water use. Despite being a torso-and-lower-body garment, the wearing verb is 着る (torso-style), since 水着 is treated as an integrated outfit rather than a pair of separate items. Japan's swimming pool and beach culture has its own seasonal rhythm, with public pools opening in summer and 海開き (sea-opening) ceremonies marking the official start of beach season in early July.