To fight this level out as a grunt soldier, you'd have to be either really good or really lucky. It's a massacre on the beach, which is exactly why you should beat the level without setting foot on the ground. Spawn as a sniper from one of the platform command posts (2,3) and walk all the way to the end of the platforms. You should have a clear shot down the dock, where many enemy units are running directly away from you, creating the perfect sniper spot. Just pick 'em off one by one. When you run out of ammo, there's an ammo droid behind you (as well as a health droid). That's really all there is to it, except for a couple precautions: first of all, don't get excited and accidentally walk off the edge of the platform. You won't survive the fall! Also, look out for the turret that sits next to the CP. If you're not paying attention, somebody will jump in it and kill you.
If you are really good, spawn as a jet trooper on command posts (2/3) and jump towards the beach. Right before you hit the ground, activate your jets and you will be safe from falling. Fly to the beach and capture it. Crouch in the water!
If you die, spawn as a soldier at the beach and stay in the water near the command post. Grenades don't work well in the water. After 2 or 3 times of this, the CIS will or will not capture the beach; it doesn't matter. Spawn as an ARC trooper in CP (2/3) and destroy any AATs or Spider Droids to help out your team. Ammo and heath droids are right behind you.