UNID Bell Oddity on 10401 kHz USB

[Antenna101]

Good evening everyone, I was scanning a KiwiSDR on the east coast of the UK when I came across a signal on 10401 kHz. It was 04:57 UTC at the time when the signal was active. This signal was active for a couple of minutes before slowly fading out and completely disappearing without a trace. The receiver was in USB mode in the recording.

The signal when seen on an SDR waterfall: it has a reverb to it and upon tuning to this signal, you hear a deep sonar like tone every 1-2 seconds. Eventually, it began to slowly fade out and at a point, it was barely audible before completely disappearing. I assumed it might have been a radio buoy of some kind, but I am not completely sure.

Here is a recording of the signal:
https://youtu.be/075rG69neyY?feature=shared