Some waters would be more dificult than others. My local Hong Kong
waters would be fairly easy. If i'm in yellow water
, i'm in the river delta
and therefore south of Hong Kong
. If the wave length is settled (ish - difficult to describe, but I know what it looks like), then I'm off the shelf and therefore 100 miles + east of Hong Hong. So if I'm appoaching from the south I stay off the shelf, cross the yellow bit, when it goes blue again and is full of plastic, turn left (that's where the sun went down).
If in the conundrum, we are permitted to use other clues, It would be even easier. China
(to the north) fishing
boats are very different to Macau (to the south) fishing
boats. Which are different again to Hong Kong fishing boats. So just by looking at the boats around me i'd be fairly confident of my lattitude.
Oh, and then there's the steady stream of container ships and planes heading to HK at 10 min intervals.........
But to treat the subject a bit more seriously, I don't think I would have too much of a problem crossing the South China
Sea to the Philippines
(500ish miles) using only my eyes to observe wind
and wave direction, the stars and the passage of the sun / moon and no other information. I don't think I'd arrive exactly where I wanted, but I don't think I'd be in any great danger
at any time.
Would be fun to try one time, just to see the result.