After hearing how treacherous walking on the reef at Niku can be, I was intrigued by a boot listed in a Patagonia catalog marketed for fishermen who wade in rocky and muddy streams. It's called the Foot Tractor Wading Boot. The unique feature is a series of soft aluminum bars on the sole that grip slippery surfaces.
http://www.patagonia.com/us/product/foot-tractor-wading-boots?p=79150-0 $279
A similar product that fits over existing footwear is the Ultralight River Crampons
http://www.patagonia.com/us/product/ultralight-river-crampons?p=79196-0 $199
Members of the onshore team might consider purchasing a pair. Even better would be if Patagonia would donate several pair. (Yes, I know time is short.)
Happy hunting.