We draw up osmosis surveys for composite yachts. In order to proof osmosis, the hull will be examined with regard to already existing damages and controlled in relation to over and underwater sections of the hull through special moisture measurements. In case that defects can already be examined visually (small bubbles), a definite osmosis deterioration can be proofed by the acid content in open bubbles. Through this method both pre-stage and damage itself can be defined exactly in order to institute adequate repair works.