Could gunfire or submarines have deepened the Taranto blow?

These are counterfactual options, not operations that occurred. One compares the gunfire option to a Mers-el-Kébir-style run, with Force A's battleships closing to shell Taranto after the air strike. Such a bombardment might have compounded the damage but would have exposed the battleships to heavy air attack during withdrawal. A second option places T-class or U-class submarines inside the harbour or off its entrance to attack surviving Italian capital ships as they dispersed. Sinking a battleship in the entrance might also have obstructed the remaining fleet. Submarine availability, clear shallow water, and the extreme risk of the mission all worked against the idea.