The Eastern Pacific - Pacific Crossing Notes: A Sailor's Guide to the Coconut Milk Run - page 262

Anchoring in the Atolls
Once safely in an atoll, sailors can head for a tantalizing, isolated motu of their very own,
even in relatively populous Rangiroa and Fakarava. But there's one last hurdle: anchoring,
which presents two sub-challenges. First, finding a well-protected spot behind the low-ly-
ing, tiny islets of the atolls can be like trying to hide an elephant behind a telephone pole.
As soon as the wind shifts, you're likely to have to move - a major effort in large atolls,
where traversing from one side to the other can be an all-day effort, and where fetch can
create considerable seas. When looking for a good spot, keep in mind that though the wind
can blow from any direction, you should be especially wary of the powerful southerly
winds, called mara'amu .
The second challenge of atoll anchoring is keeping your ground tackle from wrapping
around coral heads (bommies), since it is rare to find a broad enough sandy patch to ac-
commodate your entire scope. The solution is to “float” your chain with fenders set at inter-
vals of roughly 1-1.5 times the depth. When the chain is not under load, the fenders will
suspend it above bommies as the boat drifts from side to side. Anchoring in twenty feet of
water, for example, set your first fender at about thirty feet, the second at sixty feet, and a
third at ninety feet. Just keep in mind that a perfect set will take some adjusting after you
snorkel to observe how the chain behaves. The greatest threat comes from bommies close
to the boat, which can catch the chain and shorten the scope - just what you don't need
when a squall suddenly kicks up.