This part of the coast is fronted by extensive reefs, which render the approach to it very dangerous: at sixteen miles to the northward of the cape there is a range, the HOLOTHURIA BANKS, that extend in an east and west direction for twenty-three miles; their north-east extent was not ascertained, but the western end, in latitude 13 degrees 32 minutes, and longitude 125 degrees 46 minutes 45 seconds, is narrow, and not more than five or six miles broad.
There is another range of reefs to the westward of the cape, that extends in a north and south direction for upwards of twenty miles; and about from three to five miles broad.

The water breaks on many parts of it.

Its north extremity, in latitude 13 degrees 41 1/2 minutes, is sixteen miles West 3/4 North from Troughton Island: in this space the sea is quite clear, and from sixteen to twenty fathoms deep.

The narrowest part of the channel, between the reef and the peninsula, is at Point Gibson, where it is more than eight miles wide, and in mid-channel about twenty-three fathoms deep.
Between Cape Bougainville and Cape Voltaire is the ADMIRALTY GULF.

It is twenty-nine miles wide and twenty-two deep, independent of Port Warrender.