Thanks. You’d have thought someone would’ve heard it...
If it was large enough it would have set off infarsound sensors over a wide area, depending on where it hit in the ocean SOSUS monitors would have heard it as well. It’s unlikely people would have heard a object under a few tens of meters more than a few hundred km away. Water is a great medium for soundwaves air as well just not at the frequencies humans can hear. Low freq sounds can circle the globe in the air and water. Volcanoes routinely send sound waves around the world some multiple laps.