It's incredulous but someone actually did that successfully 10 years ago - Japanese survives diving mishap by swimming a whopping 30km to safetyMake sense, indeed.
If I were her, I would keep my mask, BCD & fins, ditch the tank & weights (assuming she did not carry any signaling devices) and start swimming to the nearest island. If she had a dive computer with built-in compass (I do), just start swimming southwards.
Coincidentally, off the coast of Kuching too.