The defence shipbuilder plans clusters in Maharashtra and Andhra Pradesh, with a proposed investment of Rs 20,000 crore over five to seven years. State-run defence public-sector undertaking (PSU) Mazagon Dock Shipbuilders (MDL), which has charted an ambitious foray into commercial shipbuilding, scouts for equity partners for proposed ₹20,000 crore shipbuilding clusters at Dighi in Maharashtra and Dugarajapatnam in Andhra Pradesh, a senior executive said.