The 'straw-bottom cruiser' in In Harm's Way

What might the film In Harm's Way mean by calling a ship an old 'straw-bottom cruiser'?

The phrase may refer to early American heavy cruisers such as the Pensacola class, whose scout-cruiser origins produced relatively light construction for their gun calibre.

The quoted phrase is unfamiliar, so the ship is checked before an interpretation is offered. Once the vessel is identified as a heavy cruiser, early American examples such as the Pensacola class become the likely model. Those ships grew from scout-cruiser ideas but received the heavy-cruiser label because they carried 8-inch guns. 'Straw-bottom' may therefore refer to relatively light construction, though the film's exact usage remains uncertain.