>>
>>(No, the answer is not 2 - see footnote 1)
>>
>>(1) Hint: Remember where he is located.
>
>Why wouldn't he climb 2 rungs, to the 3rd one, which is located 70cm above the water (before the rising tide)?

Steve,

Because he is standing on a ladder attached to the boat - as the tide rises, the boat rises and the ladder rises with it.

Regards,