Since the diver swims up 4 metres every 12 seconds, that means the diver swims up 4 * (60/12) metres = 20 metres every minute. Therefore, he will have swum up 20 * 2 = 40 metres after 2 minutes. Factoring in the diver's original position, -58m, we can calculate his position to be -58 + 40 metres = -18 metres, meaning 18 metres below sea level.
