I read from somewhere, ( could have been the prosaic The Egyptian by Mika Waltari) that almost half of the ships at that time were lost on the seas. I don't think that this would have been economically viable though as ships cost a huge amount of money/furs/beer/caps/huge stone wheels.
As far as I know, there are no shipping lists or voyage lists from the Third Kingdom available as sources, so how many ships were lost at sea would be a very difficult statistic to determine from historical evidence.
Having said that, it is possible that 50% of ships could be lost at sea without shipping becoming uneconomical. Ships last a long time if well maintained. In that time they can make many profitable voyages. Eventually, however, ships stop sailing. This can be because they were lost at sea, because they were left to rot on a beach somewhere, or because they were broken up for their materials.
It is possible that 50% of ships could be lost at sea, but shipping could still be economical as long as the average ship made enough voyages to pay for its replacement before being lost.
I very much doubt, however, if it is possible to find enough evidence to support the statistic of half of all ships in the Third Kingdom of Egypt period being lost at sea.