Firstly: The Ruling of Charity on Marine Wealth
There is no charity payable on what is extracted from the ocean, like pearl, coral, ambergris, and their like. This is by agreement of the four schools of jurisprudence, and the position held by the majority of scholars.
Secondly: Charity on Fish
There is no charity on fish when it is caught. Consensus has been quoted on this by Abu `Ubayd al-Qasim ibn Sallam and Ibn Hazm.