The moment the chaos from them diving underwater was done with, Cole could see hundreds of individual pod like submarines. Within them were black armored people, who went along with the fiery theme of the flame nation(fire nation). the water around their pods were filled with bubbles as extreme heat seemed to be boiling the water around the pods.
They were in formation, thousands of them making a net around a city under the island. However there was a dome over the sunken city, and it did not look like the flame kingdom could breach it. Which would mean that, probably the only way is from the island above itself. But that was no problem, Cole did not order the fleet to submerge because he wanted to evade the blockade, very few things can make a Raen decide to evade or circumvent. He just wanted to destroy them, and doing it from below seems to be the most viable way.
