Another of the islands famous for its grottoes is Bo Hon Island. French called it the Surprise Island. Seven of the best grottoes in the Halong Bay area are in this island. The best cave in the island probably is Hang Bo Nau (or the Pelican Cave). The cave has a big entryway with stalagmites hanging from the ceiling. It is very typical to shot a picture of the bay from the cave. This grotto is very popular among tourists. Young kids may try to sell you hand made souvenirs or postcards while visiting this site.
Other famous caves in Bo Hon Island are Hang Sung Sot, a big one that can take you up to one hour to explore; and Hang Luon, with its circular pool accessible by boat.
Not far from Bo Hon there is a smaller island with a cave called Hang Trinh Nu. This grotto is famous for its shrine. Locals dedicated this grotto to a local girl. The legend says this girl escaped from a Mandarin that forced her to marry him because her father could not pay a debt. When fishermen found her dead body, they buried her here, and built a small shrine inside the grotto.