Playing this deck, there's only one word to keep in mind: sequencing. is your greatest weapon, but also your greatest weakness. The cards you play all fit into the main idea of forcing your opponent into the sharks, but the order you play them will be the difference between victory and defeat.
There are 3 archetypes of cards in the deck: those that force movement (), those that buff your sharks (), and supporting cards to help flesh out the deck (). Playing these in a way to constantly pressure your opponent and force their moves is the best way to gain and maintain an advantage.
In addition to your sequencing, you'll want to keep a careful eye on how you are playing your sites - not only for threshold, to get a balance of Earth and Water, but also to make sure that you can give your sharks the best area of effect, while still having the ability to play your own units safely. Ideally, you can get a full row of water sites in front, while having a safe back row of earth sites to play your remaining minions to.
The main way to improve with this deck is to practice, and get as many games and scenarios under your belt as possible. I'd also recommend really getting familiar with the Giant Shark section of the FAQ and understanding the way the Storyboard works with their triggered ability, as it can really help you learn/understand how to best utilize them without hurting yourself in the process.
Remember that flooding a site does not count as a unit "entering or moving" in a body of water. You can use this to prevent your opponents from safely entering sites on their next turn, or use it as a way to get your minions onto the field safely, but still benefitting from the "body of water" mechanic (for example, or ).
This idea also extends to cards like and . Moving your body of water does not count as moving the units themselves within that body, and any units on water sites can't be buried - this gives you the ability to make some really clever positioning plays later in the game.