what does "atoll" mean in easy form
a·toll (²t“ôl”, -¼l”, ³“tôl”, ³“t¼l”) n. A ringlike coral island and reef that nearly or entirely encloses a lagoon. [Perhaps ultimately from Tamil aÚar, to be close together, thick, crowded.]
An atoll is an island formed by coral reefs which is shaped somewhat like a ring and has a lagoon in the middle of it.
Or did you mean "at all"?