Dead Island Walkthrough Part 4: Act 1 - Resort - Ch. 1 - Exodus

Talk to Sinamoi again. He will tell you that you need to find the lifeguard station and see that its safe. Accept the quest.

He will advise you to take the beach as that is the shortest way, and to radio to him once you reach the lifeguard tower.

Follow the radar and the life guard sign on the beach. You will encounter more zombies on the way, so be alert.

On the way to the lifeguard station, you will also come across Haris who is stuck in his truck and being attacked by zombies. Kill the Zombies and save him, and he will lead you to a nearby shack with plenty of items to loot and a table to repair your weapons.

Keep following the radar and you will reach some more stairs. Climb up the stairs and you will have reached the lifeguard tower. Use the security key from earlier to unlock the door.

Open the gate and kill the zombies there. Then get inside the lifeguard tower.

There will be a cutscene introducing you to a new, tougher type of zombie - the Thug Zombie.

The Thug Zombie has more health then the walker zombies you've encountered so far, so its harder to kill. However, it is also a lot slower then the other zombies. If you are having problems killing it, try using speed to your advantage by hitting it, then retreating before it can hit you, then rinse and repeat.

Also you will hear from the radio a mayday from oceanic flight 1012 saying all engines are out and they are making an emergency landing  in the jungle north of the city. This is related to a later mission. So don't go looking for it yet.

Climb up the stairs and open the hatch. You should spot the plane coming in for a landing. Explore the top floor

Look in the radar and head towards the skulls - these are zombies you have to kill to make the lifeguard station safe.

There is a room in the upper part with the radio in it. Enter it, and use the radio. Watch the cutscene. This will complete the quest, and unlock several other new missions!