Squid Girl 2 Things

Bikinis are typically two-piece swimsuits for women, available in many different styles and colors. It's like waterproof underwear.

White lab coat traditionally worn by doctors and scientists.

The character is wearing school uniform. Most probably he/she's a student.

A Swimsuit is a one-piece article of clothing that is designed for participating in different manners of water based events. Worn casually by the more modest.

Tentacles appear quite frequently in ecchi manga/anime series. They can be from monsters, animals, robots, magic, or demons. Seen as a stereotype of manga/anime.

A Yukata is a type of Kimono made of cotton that is often worn at summer festivals or after a bath in traditional Japanese Inns.