Why naval splinters could cause severe injuries

Could flying glass under blast pass through a person's body?

Yes, and both glass and large pieces of ship structure could cause extensive injuries.

Blast-driven glass could pass through a body and cause extensive injury. The term naval splinter also covered large chunks of a ship's structure. A recollection of a naval veteran's explanation contrasts these with the small wood splinters familiar from everyday work, using a large block thrown across a Napoleonic-era ship as the example.