Step 1 :Let's denote the distance from the cottage to the point P where Renee starts swimming as \(x\) (in kilometers). Then the distance from P to Q is \(3 - x\), and the distance from P to the island is the hypotenuse of a right triangle with sides \(3 - x\) and 2, which is \(\sqrt{(3 - x)^2 + 2^2} = \sqrt{x^2 - 6x + 13}\) by the Pythagorean theorem.
Step 2 :The time it takes Renee to walk from the cottage to P is \(x / 3\) hours, and the time it takes her to swim from P to the island is \(\sqrt{x^2 - 6x + 13} / 2\) hours. So the total time is \(T = x / 3 + \sqrt{x^2 - 6x + 13} / 2\).
Step 3 :We want to minimize T. To do this, we can take the derivative of T with respect to x, set it equal to zero, and solve for x. The derivative is \(1 / 3 + (x - 3) / (2 \sqrt{x^2 - 6x + 13})\), and setting this equal to zero gives \(x = 3 / 2\).
Step 4 :Substituting \(x = 3 / 2\) into the expression for T gives \(T = 3 / 2 / 3 + \sqrt{(3 / 2)^2 - 6 * 3 / 2 + 13} / 2 = 1 / 2 + \sqrt{1 / 4 + 1 / 2 + 13} / 2 = 1 / 2 + \sqrt{14.75} / 2\).
Step 5 :So the minimum possible time it will take Renee to reach the island is approximately \(1.5 + 1.92 = 3.42\) hours. Therefore, the final answer is \(\boxed{3.42}\) hours.