This is my Myth version of Portugal for the Brewing Trouble story (if I decide to include him)
He's a "Homem Marinho" (literally Marine Man), a type of merman that is completely human from the waist-up, but has 2 fish tails for legs. They're mostly known for stealing fish from lone fishermen, ruining fishing gear and boats when upset, predicting storms and having a perfect understanding of the sea currents and fish. Although their presence is rather heard than seen, their voice doesn't have the same hypnotic power as mermaids (they don't feed on human flesh to begin with)
Although they tend to avoid humans, they sometimes come to shore to sing near caves (probably because they like the echo), enjoy the warm sun and occasionally venture inland in search of sweet fruit. If caught humans often raise them as their own and teach them human language. If absent from the sea long enough the fish scales will start to fall and they'll become fully human. Their descendants (people with scaly or bumpy skin) are said to make remarkable seafarers
Apparently they were a common presence in the portuguese shores, because there were laws stating that if any dolphin, marine-man, sea dragon or any other large sea dwelling creature was ever found dead, they were property of the king and to be delivered to the authorities. And the offerings were to be given to the appointed representative so it could be delivered in mass, rather than individually (according to some descriptions they were most likely seals, rather than merfolk, but still)

So while it's highly unlikely that Port would ever be able to waterbend like that, he could probably use those 2 tails and keen knowledge of how water moves to create some serious waves =P
But although he can walk on the 2 tails as if they were legs and maneuver around land with no great ill effect, if he stays out of salt water for too long his body will start to dry and his scales falling off, in what is likely a really painful process. And considering the story takes place on dry land, with no sea in sight, he'll probably have to raid the kitchen of all the salt and confine himself to the bathroom ^^;

If you want to see a step-by-step, just go here http://birvan.deviantart.com/art/Ma.....Step-462036739