"You see some of the smaller kids go in and you think they might get hurt," says Moran, "but they just zoom around; they are so fast."
The sport was invented in Portsmouth, England in 1954. It was originally known as 'Octopush', with eight players on each team and an emphasis on pushing, rather than flicking, the puck (which was known as the squid). The sport remains Eurocentric, but is also played in parts of Asia and South America. The required equipment includes a mask, snorkel, flippers and a protective glove as well as a small stick and a puck (a lead disc).
The court area is 25 by 15 metres, with 3m gullies at each end which act as goals. On one breath, players try to anchor themselves on the bottom of the pool for up to 10-20 seconds before passing the puck to a team-mate and returning to the surface for air.
A unique aspect of the sport is the complete silence, with noise blocked out both by the water as well as earplugs and a cap.
"It's an amazing feeling," says Moran. "There is all this mayhem around you but also an eerie calm. You can't hear anything. It makes it a trust game - you have to hope your team-mates will be there because you can't tell them."
As goalkeeper, Moran acts more like a sweeper in football, and is one of the main playmakers. It is her job to receive and then distribute the puck, while her team-mates do more of the hustling and harrying, the 'grunt work'.
Aside from lung capacity, the sport requires tremendous leg power. As well as swimming down to the action and shooting back up, competitors need to be able to swim flat along the bottom. With one hand holding the stick (at just 35cm, it is more a paddle) the other arm is by your side, meaning all the movement through the water is driven by the kick.
"Your knuckles tend to get a bit munted," laughs Moran, "and the puck can sometimes hit people in the teeth, nose or face. It can also be deliberate - if someone kicks you in the ribs or 'forces' your mask off then you have to go up to the surface and are out of the match."
If you think underwater hockey is bizarre, what about underwater ice hockey? The sport is played 'upside down', on the ice under a frozen lake or pond with a floating puck. The inaugural world championships were held in Austria in 2007. The tournament attracted eight countries, with Finland crowned champions.