Found this a while back. Assuming it's saltwater based on the hooks.

https://thirstybuyer.com/products/electronic-vibrating-led-flashing-fishing-lure-w-rechargeable-usb-cable?variant=3674146406440

Theres your answer.  Its a cap for a charging port.

That's how you can tell it's a boy lure.

I think it is a plug so that you can add water to the lure for weight.  In the early 90's, there was a jerk bait on the market that had the same sort of deal, came with a syringe to inject water.  As I recall, the lure was made by Norman Lures and endorsed by Rick Clunn.   The lure in the picture doesn't look quite like the one I remember.

2 hours ago, gilkeybr said:

https://thirstybuyer.com/products/electronic-vibrating-led-flashing-fishing-lure-w-rechargeable-usb-cable?variant=3674146406440

Theres your answer.  Its a cap for a charging port.

That's definitely it.

 

I never would have guessed. I wish I had the charging cable, I'd love to see what it would do.

I remember a few years ago, a buddy of mine threw out a crankbait as the sun was going down and it was glowing blue. I was like, "what the hell is that?". It was one of those livingston crankbaits, I think Randy Howell was repping at the time. 

 

Anybody catch anything with a lure like that? I could see how it would help for night time fishing, but just seemed like a fisherman trap.

1 minute ago, MountainMan83 said:

I remember a few years ago, a buddy of mine threw out a crankbait as the sun was going down and it was glowing blue. I was like, "what the hell is that?". It was one of those livingston crankbaits, I think Randy Howell was repping at the time. 

 

Anybody catch anything with a lure like that? I could see how it would help for night time fishing, but just seemed like a fisherman trap.

I experimented with glow-in-the-dark stuff a while, fishing right before daybreak, and I eventually came to the opinion that it scares fish. Maybe it works in some areas where there are edible bio-fluorescing food sources, but I gave up on it.

I have some deep diving livingston lures that its eyes glow purple/blue along with the baitfish noise.  I've caught fish but nothing too crazy to set it apart from a normal diver.

So baits are now having bungholes on them? ?