Why submarines did not wait outside Taranto

Was a simultaneous submarine strike considered during the Taranto raid?

Not inside the defended harbour, and boats that might have waited outside were limited and committed to other Mediterranean tasks.

The harbour's defences made a simultaneous submarine penetration unattractive. Boats stationed outside might have attacked ships leaving after the air strike, but British submarine numbers were limited and other Mediterranean tasks competed for them. They were already attacking Axis logistics, gathering intelligence, and supporting special operations. An apparently obvious follow-up therefore carried a real opportunity cost.