empilement/couches de récif (coraux)
Libre choix de formulations possibles...

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Explanation:
"Reef pilings" doesn't seem to be a recognised term, just something put together by the author of your text. As your text seems not to be at all academic or technical, it is reasonable to assume that the author had only a fairly foggy idea of what he or she meant by "reef pilings". The most one could say is that they mean vertical elements of a reef. If you refer to the reference cited below, you will see that "piles" used in association with reefs are generally piles of debris that might form a core for a reef, or piles of debris (including dead coral) left behind when a reef has died. It's unlikely that would give a positive message to tourists, which again indicates a non-technical and rather clumsy use of language by the author.


Reference: http://geology.uprm.edu/Morelock/concept.htm

une suggestion...

si les récifs sont en corail

ou du rivage corallien

I think it matches the idea in the source text, and it is a phrase that is used in French (see for example ref. p. 11)

Une manière détournée de prendre en compte les infos d'Alison en référence (on peut le comprendre au sens propre et au sens figuré).
- les pilotis du 'wharf'
- 'reef' dans le sens d'une barre d'obstacles submergés (près de la côte)