These very high level troops can only be trained in a water outpost equipped with a level 10 training camp. This means you must have a completion grant in addition to the following minimum requirements:

Clairvoyance Lvl 4
Factory Lvl 7
Food 4,000
Idle Population 10
Lumber 5,500
Metals 2,500
Metalsmith Lvl 7
Rapid Deployment Lvl 8
Stone 7,000
Training camp Lvl 10

'Because the Fangtooth are water breathers, you must have a Fangtooth Respirator (found in lakes level 7 and above & camps 7 and above ) for each one you train. When a Fangtooth dies, you do not get the respirator back. You also may purchase respirators in the Shop.'You also get 500 Fangtooth Respirators as a reward for upgrading your training camp to level 10.