The natural resistance of ten species of timber suitable for catamaran fabrication was evaluated at Visakhapatnam and Kochi harbours to suggest suitable substitutes to the conventional species as their availability is fast dwindling and prices are soaring up. The results showed that none of the ten species exhibited any remarkable resistance against marine organisms attack. The timbers lasted at the most for 9 months at Visakhapatnam and 7 months at Kochi. While the destruction of panels at Visakhapatnam was caused exclusively by teredinids, that at Kochi was brought about by both teredinids and pholadids. From the study, it is seen that preferred species did not offer any specific advantage over the underutilized species tested. Therefore, it is emphasized that any timber species used for catamaran fabrication be treated with suitable preservative chemicals so as to obtain long service life, saving of expenditure and conservation of forest wealth and its biodiversity.