Mia Knight, 16, is believed to have fallen unconscious while swimming in the sea at Portimao in Portugal on Wednesday. It is believed she was due to collect her GCSE results on Thursday.
Tributes have been paid to the teenager, who went to Hove Park School in Hove, East Sussex, on Twitter.
One, from Josie Milligan, said: “RIP Mia Knight, so sad to think such a young life could be lost: Much love to the family. Will miss you Mia, never forgotten!”
Another, from Ashleigh Messer, read: “RIP Mia Knight, you beautiful girl. You will NEVER be forgotten, one of the loveliest girls I’d ever met. Still can’t believe you’re gone.”