The deepest port of India is

Concept

India's major ports fall broadly into two kinds: natural harbours, where coastal landforms already provide a sheltered, deep basin with little need for dredging, and river-mouth or artificial harbours, maintained through engineered channels in shallower, silt-prone waters. Static-GK material on Indian ports ranks ports by this natural draft (depth), and the port with the greatest natural draft among the major ports is the one conventionally cited as India's 'deepest port'.

Application

Applying this to the four ports offered here:

• Vishakhapattanam (Visakhapatnam): a natural harbour enclosed by the Dolphin's Nose and Ross Hill headlands, conventionally cited in Indian exam GK material as having the greatest natural draft of any major Indian port.

• Paradeep: a river-mouth port at the Mahanadi delta, developed mainly for iron-ore and coal exports, requiring regular dredging to keep its channel navigable, so its natural draft is comparatively shallow.

• Haldia: a subsidiary dock on the Hooghly river downstream of Kolkata, also requiring regular dredging because of silt deposition, so its natural draft is comparatively shallow.

• Cochin: a natural harbour too, but on the west-coast backwaters, and it is not the port this GK convention cites for the greatest depth.

Since Vishakhapattanam alone matches the "greatest natural draft" criterion among these four, it is the deepest port of India in this listing.

Cross-check

The Tripura Public Service Commission's own official final answer key for this exact question (Sub Inspector Excise 2014) also keys it to Vishakhapattanam, and independent Indian competitive-exam GK compilations state the same fact, corroborating the result.