I've had this feeling a few times while swimming. One, I can still remember after almost 30 years. It still creeps me out. Not that I feared a shark attack. Just a sense of dread. Plus thinking of how far from shore I was.
I’ve had that feeling just before all the bait fish started jumping straight out of the water all around me. That probably wasn’t a shark, it was probably a barracuda. I’ve also had a bottlenose dolphin leap out of the water and splash down not ten feet away during one of those creepy moments. I’ve often wondered about that, given dolphin behavior toward sharks and toward humans. I might owe that dolphin a thank you.
My wife and I had this horrific dread set in on both of us on two occasions. Once was in Mexico at one of the old ruins. There was a particular area near a shaded part of jungle. We walked towards it and then it set in. We turned around wondering WTH? We discussed it and both of us truly felt a tangible..."sense of dread" or "very, very bad" feeling. I started walking slowly towards the area again with my wife in a better place close to other people and I felt it set in again. I had never felt anything quite like it.
A second time was in the forests near Flagstaff AZ. We were pulled over to the side of the road walking in a heavy pine wooded area. The feeling that set in about 100 feet in was not "dread" but a sense of "flight, like right now". I am not taken to panic but it was bad.
In contrast my wife and I had a "We're probably going to die, call the kids" experience together years later. Without going into too much detail, it was a chance event and bad timing. What at made me happy is I was able to put everything in God's hands and accept that this could be the end. I was actually calm and even toned. I called our kids and gave them instructions. My wife put her head against my shoulder and held my arm while I comforted her and we waited. Then it was over and we were still alive.
I did not feel that sense of dread, only the realization that we could easily be dead in seconds or minutes.
Man, did I ever score points with my wife.
Anyway, I can't ever discount that there are deeper forces that compel us to react and respond to different situations. You were right to feel the way you did and respond that way. Glad it worked out well for you!
So did you get out of the water?
I had that feeling at least once. I ignored it, and moments later I was being held up, with a gun to my head.
Sort of like the feeling of dread stepping on the scales in the morning.