This invention provided a high-build, self-polishing marine antifouling paint which affords a coated film having antifouling properties for a long period of time. The paint binder which is a fiber reinforced aldehyde resin comprises two synergistically acting components, Component A and Component B. Component A an aluminium di-sec-alkoxide ace-toacetic ester chelate is represented by the following formula (1): (R.sup.1O).sub.2--Al--(CH.sub.3--CO--CH.sub.2--CO--O--R.sup.2) wherein R.sup.1 represents an sec.-alkyl group having 3 to 10 carbon atoms, or a cycloalkyl group; and R.sup.2 represents an alkyl group having 1 to 10 carbon atoms, or a cycloalkyl group. Component B a monoalkoxy organo-titanate0IV is represented by the following formula (II): R.sup.3--O--Ti(--X)3 wherein R.sup.3 is a monovalent organic group having from 2 to 30 carbon atoms or a substituted derivative thereof X in the above formulae independently represents an acylate group, a sulfonic acid reside, a phosphoric acid residue or a pyrophosphoric ester residue, or a mixture thereof.