Maybe its a hook used by a helicopter to grab rope or cable like a water bag for fire fighting. It looks like the clamp on the end may have been a break away bolt connector.
Wonder if it could be an aircraft carrier cable stop, or maybe tool for dragging through water to grab a cable. It sure seems like something to do with large cables. Does it look like it could of been set to have a closing lock attachment. Can't tell from pic looks like it's new or been polished. Cool find though, hope you find something info.
Good luck, L8s