Possible Middle Reader: Title possibly has the word Dragon in it

[Susie]

Have a middle school student trying to find a book and this is what she is able to remember:

The word Dragon in the title although there are not dragons in the story except maybe at the very end.

Main character is a boy at boarding school. He makes some friends, boys and girls and they go on a quest.

He is able to breathe under water because of a pearl he puts in his mouth. There are also gills, (sleeves? tatoos?) that he wears on his wrists, he takes them off and gives them to one of the girls.

Does this ring a bell for anyone?

[Ayshe]

Something from the Beast Quest series by Adam Blade maybe?

Solak Scourge of the Sea and Sepron vs Narga at least appear to have the magical Pearl of Gwildor which allows the bearer to breathe beneath the water: https://www.google.com/search?tbm=bks...

[Lobstergirl, au gratin]

Susie, are you still looking for this or did you find it?