A promise as deep as the sea

It's a known fact that sirens sink ships. But when Prince Alfred goes off on his own in attempts to sink a vessel, he picked the wrong person to attack! Captured and brought on board by Captain Bonnefoy, Alfred is giving two choices: Help him steal treasure from his own home, or death. But as fate would have it, there would be a lot more waiting down the road. Yaoi, FrUs. MA