The correct option is
B ensconces
The line states- 'or secretes himself near the shores of rivers, bays and lagoons of thickly wooded and uninhabited countries...'
We can understand that he settles near the shores of rivers, bays... Let's see which of the following words mean the same.
Option A - 'Admit' means to allow someone to enter a place. Here, he enters the place himself. Thus option A is incorrect.
Option C - 'Emanates' means to express a quality or a feeling through the way you look and behave. As the sentence is not about behaviour and appearance, we can't use 'emanates' here. Thus option C is incorrect.
Option D - 'Entertains' means to keep someone interested. 'Secretes' definitely has nothing to do with keeping anyone interested. Thus option D is incorrect.
Option E - 'Silences' means a complete absence of sound. As the sentence is about settling and not silencing, we can't use 'silences' here. Thus option E is incorrect.
Option B - 'Ensconces' means to make yourself settled and comfortable in a place. 'Secretes' also means to settle somewhere comfortably according to the given passage. Thus option B is the correct answer.