The answer to this can be found in Chapter 10 of The Swiss Family Robinson, at least in the version summarized by eNotes. In the version available on Gutenberg, the answer is to be found in Chapter 4. In either case, the answer is that the family names the bay “Safety Bay” in order to express their thanks to God for saving them from the shipwreck.
The Swiss Family Robinson is a great adventure book, but it is also one that was written largely to educate and improve people who read it. The father in the book is constantly teaching his children. He wants them to learn all sorts of worldly subjects, but he is perhaps even more interested in teaching them to be good Christians. He speaks to them very often of how grateful they should be to God for all the ways in which he has blessed them. His wife often joins in teaching their sons this lesson. Naming the bay “Safety Bay” was part of this effort.
As we can see in the appropriate chapter of the book, the boys suggest other names for the bay. They want to name it after the oysters found there or the lobster that bit one of them there. However, the mother reproves them. She says she thinks
that in token of gratitude for our escape, we should call it Safety Bay.
Thus we have the answer to the question. The family is grateful to God for allowing them to escape safely from the shipwreck. Therefore, they name the bay after safety, rather than after any of its natural features.