It is hard to beat Strand of the Ancient in under 4 minutes, especially for Horde (This is for HORDE).
What you need to do is team up with other people and capture under 4 minutes, when the next turn begins, jump off of the boat and swim to the nearest island. Wait there and when the match ends, jump into the water where the boat path is. We didn't capture the relic but we still got the achievement.
by wyldd00d