Sounded like the first recording link above of toad fish, but the silhouette, wake it was making on surface looked too big for that... Was just after sunset... not much more I can remember, been searching the net for information or similar experiences but not much out there... Here is what I wrote it down when memory was fresher. Hope SDR add his details to this story...recounting..
"We’re standing at the water’s edge, watching the last seconds of a breathtaking sunset, and hear some light splashing a few feet away, a small four foot or so shark is cruising up the shallows towards us and his dorsal and tail are sticking high out of the water. We’re still excitedly talking about how cool that was when in from the opposite direction we started hearing what sounds like a muffled fog horn approaching. The next moment we’re seeing the up-flow billowing telltale rippling of a giant slow moving fish coming our way. It swims right in front of us making a mysterious fog horn noise which resonates in our chest with deep vibrations. It is really big and I guess from its size and silhouette, a giant jewfish, but Sean’s insisting that it’s a big drum,,,."