1.0 Introduction There is a substantial interest in implementing wet welding for structural repairs of offshore installations. Some of the restrictions to its use are heat affected zone (HAZ) hardening and cracking, and the inability to produce wet welds that meet the bend test requirements of a surface weld. Restrictions to the application of wet welding are even more sever in the North Sea where high strength, high carbon equivalent structural steels are used. A reduction of the diffusible H2 contents of wet welded joints (i.e. lower risk of H2 induced cracking) would certainly lead to a re-evaluation of the process regarding its practical application, especially considering high carbon equivalent steels. This is more so in face of the acceptable mechanical properties and low defect rates achievable with some of the electrodes presently available. Such desirable reduction in the weldments H2 content could be achieved through an "in-situ" (underwater) post weld heat treatment (PWHI). In order to evaluate the feasilibllity of such heat treatment method a series of tests has been carried out in which bead-on-plate welds have been deposited on high carbon equivalent base plates and then submitted to different "in-situ" heat treatment procedures. This report presents the results of these preliminary investigations. 2.0 Theoretical Background Due to the fast cooling rates and the high hydrogen content, characteristic of weldments produced in wet environment, hardening and cold cracking in the HAZ and weld metal are possible, especially in the case of high carbon equivalent steels (CE > 0,40 %) /1/. Postweld heating methods have been investigated in order to improve the mechanical properties of underwater welds 12,31. One way to prevent cold cracking in underwater welds is to facilitate the diffusion of atomic hydrogen by heat treating immediately after welding. Suga /2,3/ investigated the effect of post-weld heat treatment on the occurrence of cracks and on the evolution process of hydrogen out of the welds using beadon-plate runs (13Omm in length) deposited underwater. After removing the slag, the test plates were immersed into an isothermal bath within 60s after completion of the welding. The test plates were kept in the bath for J)l'eset times, then cooled in water and left in air at room temperature. Suga /2,3/ obselVed the occurrence of under bead cracks in the HAZ of underwater welds within a period of about 5 min. after welding. His observations stated that under bead cracks as well as root cracks could be prevented by "in situ" PWHr above temperatures of 100 DC with appropriate holding times. Similar results have been achieved by Ibarra et. al. /4/ using the multiple temper bead technique. This technique involves immediately placing a second pass over the previous one to soften the hardened HAZ and eliminate hydrogen. The experimental and practical results obtained indicated that this method was successful in assisting hydrogen diffusion out of the weldment /5/.