This chart shows the entrances to the Bay of Tayouan (up is north). Between Zeelandia and the crooked island just above it was the deepest and widest entrance (the numbers are depth measurements), which was guarded by two fortifications: Fort Zeelandia and a smaller redoubt known as Zeeburgh. When Zheng Chenggong invaded Taiwan, he was able to avoid the main channel, since his junks did not draw so deeply as European ships. Instead, they entered by means of shallower channels, safely out of range of Dutch artillery. Used by permission of the Austrian National Library (finding aid: Atlas Van der Hem, V. XLI, sheet 4-2). Source: Austrian National Library, Atlas Van der Hem, V. XLI, sheet 4-2

From How Taiwan became Chinese: Dutch, Spanish, and Han colonization in the seventeenth century by Tonio Andrade