The Blue Dam is located on the east side of Mota. As a result, there's no town located particularly close to the Blue Dam that makes it an obvious starting point. You could either:
Start in Kueri, jump on the Jet Scooter and travel west across the ocean when you reach the canal that led to the Yellow Dam,
Start in Piata, and work your way back to the west coast before jumping on the Jet Scooter and riding north until you reach the canel that leads to the Blue Dam, or
Start in Paseo, travel north to reach the Jet Scooter, and then follow the coast clockwise until you reach the Blue Dam canal.
No matter what method you choose, it's going to be a bit of a hike.
The Blue Dam consists of 5 floors. Not only will it see you travel from the first floor to the fifth, then back down to the first, and then all the way back up again, you'll need to strategically drop down particular holes in the floor. As a result, a floor by floor walkthrough is difficult to provide, so a more comprehensive step-by-step walkthrough is provided below the maps. Throughout the Dam, you will find a number of helmets that provide good defense, but also have the ability to cast valuable spells when used as items in battle.
The following walkthrough describes how to efficiently proceed through the dam and reach the control panel, while picking up all of the treasure chests along the way.
F1 - In the entrance, use the Blue Card to unlock the door to get inside.
F1 - (Optional) Take the chute below the entrance to the second floor in order to collect an Antidote from the chest, and then return to the first floor.
F1 - Head left and then up to the next chute which leads to the second floor.
F2 - Follow the path down and to the right to the next chute up to the third floor.
F3 - Follow the pathway to the left as it dips down and then back up again. Pass the first chute up, and enter the chamber above to access a chute that leads down to the second floor.
F2 - Collect the Crescegear that you can find in this room. The Crescegear is decent head protection for Rudo, but it also doubles as an item like the Amber Robe that can restore 60 HP to the holder when used in battle. Return to the third floor.
F3 - Head back down and take the chute that you initially passed, up to the fourth floor.
F4 - Travel a short distance to thr right to reach the next chute that leads to the fifth floor.
F5 - Head down and to the right a bit. On your way to the next chute, you will find a chest that contains a Storm Gear. While it provides good head protection for Kain, it's true value lies in its ability to cast a modified version of Gizan. When normally cast by an individual, Gizan can only deliver wind damage to all enemies of one group. But when deployed by using a Storm Gear, it affects all enemies on the screen, not just one group. If you have a weak fighter in your group like Amy, giving Storm Gear to her and letting her use it in battle will transform her into a reliable damage dealer. Once you have the gear, continue on to the chute below, and travel to the fourth floor.
F4 - You will find yourself in a room with five pits and a chest to your right. First, collect the chest. In it, you'll find the Color Scarf which offers head protection Anna. When used in battle, it can cast Saner, which increases the Agility of all of your party members in battle. Don't bother with the chute that leads back up to the fifth floor; it only leads to a dead end. Instead, drop down any of the three right holes in the floor (the two on the left will force you back to step 7).
F3 - You will land near another chest. This one contains a Snow Crown, which can be given to Amy for protection. When used in battle, it casts Deban, a spell that increases your allies defense against enemy techniques. Collect it and proceed to the next chute below which takes you back to the second floor.
F2 - Walk to the left until you reach a chute that will take you down to the first floor.
F1 - From where you arrive, you must walk up and out of the chamber, before heading left and back down the left side of the floor, before ultimately reaching the bottom and heading right to find a chute that leads back up to the second floor.
F2 - From where you arrive, walk up and use the chute directly above you to the third floor.
F3 - Grab the chest in this small chamber to find a Wind Scarf, head protection for Shir. This scarf can also cast Zan when used in battle, which does a small amount of wind damage to one group of enemies. Collect it and return through the same chute to the second floor.
F2 - Walk to the left and then up to reach the next chute that takes you back to the third floor.
F3 - Follow the path up along the left side of the floor to reach a chute that sends you to the fourth floor.
F4 - From where you arrive, ignore the chute to the right which leads to a dead end. Instead, head down, and then to the right until you find a chute that sends you to the third floor.
F3 - Take a short trip down to find another chute that sends you back up to the fourth floor.
F4 - Be sure not to fall through the hole in the floor to your left. Head down and bit and investigate the chest to the left to find a useful Trimate. Then walk all the way to the right, then up to the top, and back to the left to find a chute which leads to the fifth floor.
F5 - Head down, left, and down again to find a chute which returns you to the fourth floor.
F4 - Take the chute immediately below you to investigate part of the third floor.
F3 - In this locked off chamber, you'll find a chest containing Star Mist, a rare item that can fully heal all of your allies. Then return to the fourth floor.
F4 - Head left until you reach the chute that will send you back up to the fifth floor.
F5 - Walk up until you see holes in the floor. Drop down any one of them to the fourth floor below.
F4 - You should now be standing on the platform with the control panel. Use your Blue Card to open the gates of the Blue Dam, and allow more flood waters to reach the ocean. Now exit out of the Dam by any means.
