Be sure to get the Pikmin 3: Prima Official Game Guide.
By the time you reach the Armored Mawdad, you should have a decent supply of Red Pikmin and Rock Pikmin. Try to bring a full squad of 100 Pikmin, divided evenly between these two Pikmin types.
The Armored Mawdad’s attacks are fairly limited, but they can be very effective. This beast charges along the ground, using its giant pincers to trap any creatures unfortunate enough to be in its path. The Armored Mawdad snaps its pincers before each charge—each time you see this warning, move quickly to lead your Pikmin out of the way.
The strategy for defeating the Armored Mawdad is fairly simple: throw Rock Pikmin to shatter its protective crystal plates, then use Red Pikmin to attack its exposed flesh. The armor protecting its head is very thick. The armor at the tip of its tail, however, is much easier to break—try to focus your early attacks there. If its tail is out of range, just chip away at any bit of armor you can reach.
Each time you shatter one of the Armored Mawdad’s plates, the creature retreats a short distance. Any attackers caught in its path will be knocked to the ground, so try to stay out of its way. Lock onto the Armored Mawdad and position yourself so that the creature's exposed flesh is directly in front you. Send your squad charging in to attack. With a little luck, your Red Pikmin will be able to do a considerable amount of damage before they’re knocked loose.
After each attack, collect as many idle Pikmin as you can. When the Armored Mawdad takes enough damage, it climbs up the walls and scurries out of range of your attacks. Use this time to round up your scattered Pikmin, and use the debris falling from the ceiling to track the Armored Mawdad’s position.
If you’re knocked to the ground, waggle the Left Control Stick (or the Nunchuk Control Stick) to get back on your feet. The Armored Mawdad attempts to devour any Pikmin it manages to catch. To free trapped Pikmin or crew members, use Rock Pikmin to shatter one of the Armor Mawdad’s crystal plates, or use Red Pikmin to deal enough damage to send the creature running.
Keep your Pikmin out of harm’s way, and chip away at the Armored Mawdad’s health until you complete the encounter.
Ready for more? Get the Pikmin 3: Prima Official Game Guide.