This is no unusual effect in such instances.
On we glided, within less than a cable's length of the shore which was margined with foam that sparkled all round.

Within, nestled the still, blue lagoon.

No living thing was seen, and, for aught we knew, we might have been the first mortals who had ever beheld the spot.

The thought was quickening to the fancy; nor could I help dreaming of the endless grottoes and galleries, far below the reach of the mariner's lead.
And what strange shapes were lurking there! Think of those arch creatures, the mermaids, chasing each other in and out of the coral cells, and catching their long hair in the coral twigs!.