trident returning sound

While playing I have heard this sound on 2 occasions. 1st time. My villagers from my village breeder had accidentally been turned into zombie villagers, I decided to cure them and I went to get the things to do that. I started hearing a trident sound, my subtitles said trident returning. I heard the sound on repeat for about 10 to 20 seconds, quicker than if a drowned was firing tridents at me, I looked around, but couldn't see a drowned, I base near a river and I don’t think a drowned can spawn in a river. When I want back to the zombie villagers they had all de spawned, I hadn’t traded with them, I thought they would have been persistent. I thought the sound I heard was them de spawning?

2nd time. I was building and had been breaking some blocks, the sound happened again, for a similar amount of time as before. Again I looked around and there was no drowned or trident, it was day time though. My villagers are more secure and were all there, as were the other mobs at my base.

Although I’m playing vanilla, I do have data packs from Vanilla Tweaks, anti creeper grief, armour statues, cauldron concrete, cauldron mud, double shulker shells, dragon drops eltyra, more mob heads, silence mobs and silk touch budding amethyst. I do also have some 20 resource packs, mainly visual but also quieter minecarts and quieter nether portal.

I’ve played on this world for just over 200 days and only heard the sound twice.