Noise from my SQ5 after going through shallow flood water

Hi, I wondered if someone could possibly shed some light on my SQ5 problem.

I went through some flood water just before this currant lockdown, water depth was around 7 - 8 inches & i drove through it at a steady continue speed.

After I had driven through it I went to my sons which was about half a mile from the water.

When I left my sons I had my windows down & I could hear what I can only explain like water moving around, it only does it when moving the car even at low speed.

I have been shielding since the lockdown started this year & the first time I went out in the car was last Wednesday 10th Feb to get my covid jab .......... Well buggar the noise was still there, I just have no idea what is causing it.

I thought it might of been water trapped in the plastic belly pan cover or like and not draining because of blocked drain holes. also sounds like water in the tyre which I know is ridiculous.

any advice would be much appreciated.

Regards & Stay Safe All