Dear All,   Greetings. We are looking to buy a second-hand or used (simple) hydrophone for educational purposes on board research-based whale watching operations in Mazatlan, Sinaloa, Mexico. Help will be much appreciated in locating individuals or research groups that might know about some opportunities. Please reply directly to sender.   Thanks a lot in advance! Oscar Guzón (M.Sc.) Director General Onca Explorations S.A. de C.V. Río de la Plata 409 Col. Gaviotas 82110 Mazatlan, Sin. México. Tel: (669) 913-40-50 Movil: (669) 116-03-01 Email: oxinfo@gmail.com www.whalewatchingmazatlan.com