A dinosaur couple, Blimpy and Cheeks, heard about there potentially being treasure in a ruined temple on the seafloor. While they don't have scuba gear or the money to afford some, they can both hold their breath for long enough that, in the past, it hasn't mattered. If it'll ever matter that they need air, though, it'll be on this extreme dive...

Suggested by https://rekstone767.deviantart.com/
Blimpy and Cheeks are their characters, and can be seen here: https://www.deviantart.com/rekstone.....heek-998019216