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Well from the physicist point of view its negative (due to the co ordinate system) but this is real life and depths aren't measured to be negative. So go for positive!
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I'll choose the negative
I guess there was more information to solve it? I don't know. Anyway, I would guess "positive." I'm not 100% on that, but
1. Depth was measured to b 2.0m, so it will not look inverted, like -1.5m.
2. If it is a quantity irrelevant of sign, it would be used as positive, right? Like, distance between two point with no specified coordinate system.
3. Wikipedia pointed me to a convention of measuring depth in a well. Down is the positive direction. Makes sense for the pool, too, I guess.
"Sign Convention - Depth increases positive in the downward direction."