Look up the sleep tracking accuracy for the Samsungs (and most smart watches). Quantified Scientist on Youtube.

100% recycled plastic wouldn’t look bad though…

3000 grit sandpaper

Not advised for the Series 9, but it CAN do 50m. The issue is that the waterproof seals do wear out over time and 50m repetitively will accelerate that degradation significantly.

The Ultra 1 & 2 are designed for extended use at depths of 40m and will survive 100m.

Here’s a link confirming the above.