It's an intriguing explanation. It's not like the Mediterranean Sea is devoid of shipwrecks. Quite the opposite. It's been too long since I last listened to Mike Duncan's History of Rome podcast, so I can't recall the particulars of what else was happening when the Pantheon was built. It could also have been as simple as a budget shortfall, although it is unwise to scrimp when it comes to deities if you're a believer in the Roman pantheon, so that's unlikely.