u/According-Garlic-482

A 90s/early 2000s children's book about a boy called Tom, who's mum keeps pushing him to do competitive diving, even tho he doesn't want to. One day he has an accident while driving and ends up in a coma. While in his coma, he dreams about a land of twins, if I remember rightly. When he wakes up, he tells his mum and she tells him, he was a twin, but his twin died at birth, if I remember rightly. I borrowed it from the children's section in our local library when I was a teenager.