Forever 21 chunky platform slides in blue. They feature a distinct puffy thong-style strap and a lugged, platform sole. 

Poshmark +1

While these specific Forever 21 slides are frequently found on resale platforms like Poshmark for around $35, several luxury and lifestyle brands offer very similar "puffy" platform styles:

• GANNI: Offers a highly similar "Padded Thong Platform" sandal in blue.

• UGG: The "Aww Yeah" platform slide provides a similarly bold, chunky aesthetic in vibrant blue.

• Balenciaga: Features high-end leather platform slides with a similar silhouette.