Plane of Water Subjective Directional Gravity

[Fedor Checherov]

Paizo PRD says that Plane of Water has
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Subjective Directional Gravity: The gravity here works similarly to that of the Plane of Air, but sinking or rising on the Plane of Water is slower (and less dangerous) than on the Plane of Air.
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But what is the speed of a character sinking in the direction of his Subjective Directional Gravity? 145 feet/first round is slower than 150 feet/first round, as well as 5 feet/first round - but there is huge difference between these "slower" numbers

[fearcypher]

With a lack of RAW on the topic, I would suggest either 75 feet or 35 feet.

Those numbers line up with the difference between normal speed and swim speed, so realistically it would make sense.

Just my two cents if you had to make a ruling, considering the lack of RAW.