This verse is a highly poetic metaphor comparing the spiritual darkness of disbelief to the immense, frightening depths of a tempestuous sea. The 'layers of darkness' and 'waves upon waves' evoke the profound, inescapable nature of being lost at sea—a powerful image for 7th-century Arab traders. Reinterpreting this spiritual metaphor as an explicit reference to the physical phenomenon of 'internal waves' (subsurface ocean stratifications) requires stripping the verse of its literary context. Classical scholars like Ibn Kathir interpreted this solely as a parable illustrating the compounding ignorance of the disbeliever.