Thanks to Kevin Preuss and Dave Lehmiller for this identification :
" it looks like the true H. caribaea which I saw on the Florida Keys on the beach. " (K.P.)
" The Hymenocallis is the same one I observed growing along the beaches [in the Seychelles]. It is a naturalized alien of recent origin -- Baker did not list any Hymenocallis in his 1877 book, nor any Pancratium. " (D.L.) See : D.J. Lehmiller, 1988. Crinum of the Seychelles and Mauritius. Herbertia. 44(1): 13-16. [" many beach on Mahe are currently rank with Hymenocallis, probably H. caribaea."]