Little published research on transportation of works of art by sea includes the results of monitoring the environmental conditions actually experienced. This article describes how two large tapestry cartoons by François Boucher were shipped as deck cargo from London, England, to Muizenberg, South Africa, in an insulated container during May-June of 1989, with the environmental conditions within both the container and the envelope of the packing case continuously recorded. Although the external temperatures varied from 15°C to 31° C in the tropics, the relative humidity of the air space containing the paintings changed slowly from 70% to 75% over the last 13 days of the voyage. Such stable conditions are rarely achieved by other modes of transportation.