Brainteaser: The man on the paddle boat

A man, an environmental activist, wants to hang a banner to
send a message to stop the over-fishing of tuna fish. He thinks
that hanging the banner on a fishing boat anchored near a
fisherman's village is the perfect spot to send his message.

The man uses his small paddle boat to approach the larger
fishing boat unnoticed. He plans on climbing up the fishing boat
using a rope ladder that hangs on its side.

To his dismay, the bottom of the ladder is three feet above his
extended arms. There is nothing on the paddle boat he can
stand on to extend his reach. He cannot jump up to grab the
ladder because his boat is small and light, and will become
unsteady in the water.

Then, he figures that the tide is rising at the rate of one foot per
hour. His paddle boat will rise with the tide, and if he waited long
enough he should be able to reach the bottom of the ladder.


How many hours would he have to wait at sea for the tide
(water) to rise high enough so that he could grab the ladder?