Loud bubble sounds from the sea?

Back in 1994 i was hiking Cumberland Island national seashore. Most of the hike was along the beach during march, and the weather was quite pleasant. My group became a bit scattered as we hiked, all just enjoying the serenity of the ocean. As I was walking a kept hearing a strange sound. A loud sound coming from the sea.

The best way I could describe it is the sound the tub makes when you pull the plug from the drain to let the water out. A loud “GLUG” sort of sound…but with a pronounced echo. Maybe yet another, more amusing way to describe the noise (and I’m dating myself here) is the sound Sonic The Hedgehog makes in the underwater levels when he runs out of air. The pitch was actually fairly close to that.

At the time, I thought it was pockets of gas escaping from under the sea bed or whales or something, though it seemed awfully loud for either of those things. It was creepy. I know about the see “bloop” that has been recorded by underwater microphones(https://en.wikipedia.org/wiki/Bloop), but this was clearly audible from land. This has been bothering me for years. Any ideas as to the source of the sound?

For your edification:https://www.youtube.com/watch?v=pRPv_MMB_Rk

A 16 second clip featuring sonic the hedgehog drowning. The video is of poor quality, but you get the idea of what the sound was like.

The bloop was an underwater phenomenon - if you heard something from the shore, it must really have been a surface phenomenon (as sound does not transfer from water to air very well).

I suggest this could have been waves or swell lapping into a hidden cave or other shoreline feature.

How timely. Maybe it’s this?

Mystery behind bizarre ocean quacking sound unravelled. Zee News (India), April 23, 2014.

hmmm. Well, the sound that i heard does not really match that one.

I guess i have to concede that it was UFOs. Yes, that’s it, UFOs…