info on drowning tragedy in Frierfjorden, Kragero?

I am looking for more information on a boat accident that occured on 21 Jul 1829 in Frierfjorden, Kragero, Telemark. In arkivverket 1829 p. 237, http://www.arkivverket.no/URN:kb_read?show=121&uid=39164&urnread_imagesize=full&hode=nei&ls=1 Isach Gundersen and one of his three daughters, 8 year old Marthe Helene Isachsdatter were drowned with two other men and the wife of one of the men. Is it possible that there is more information out there other than the information listed on the death entry for Kragero? Was it a ferry, or some other public conveyance? Were other people on board who were rescued? Drownings of fishermen at sea were a frequent tragedy in this area, but as there was a woman and a child, and possibly other people on board, this is unusual, and may have been reported in some book elsewhere. I would like to know more about this, if possible: Isach Gundersen was my g-g-g-grandfather, and it is possible that his wife and two other daughters (my g-g-grandmother were on the same boat but survived. Thanks in advance for any help