[causi]

If it supports very little life then there's very little life to die there and sink.

[kuhewa]

Generally the oxygen minimum zones aren't extending up into the photic layer near the surface which does support a fair amount of life.

[zeristor]

There’s Oxygen near the surface just not further down in the depths.

Whales could swim through an area since the surface to breathe, but could pop their clogs at any time (I assume).