Athletics - Swim

Like running, swimming is something everyone should be able to do without a check, unless put under some sort of stress. As soon as there are conditions that make swimming dangerous, or if the character’s performance matters, the character must make a check. 
The difficulty of the check is based on the strength of the currents and waves.
Even though swimming during a structured encounter brings a strategic layer to it since it dictates how much a character can move in a given round, making successive checks in narrative scenes can grow boring pretty fast.
Imagine a party of four characters that have to swim over a Long distance. Considering they are not rolling t to treat water as normal terrain rather than difficult, it would take each character a minimum or two rolls to get there. Chances are, some characters are going to be bad at swimming and will require three or more rolls. That's a lot of swimming checks to make and people around the table might grow bored as it slows down the narrative.
Therefore, this author recommends making a single check per character that will cover the whole distance. On a successful check, the character reaches their destination. On a failed check, either the character reaches it anyway but suffers heavy strain depending on the distance, or make checks until that character succeeds at least once. When making a single check for extended distance, this author recommends increasing the amount of strain suffered by the character on h symbols.
EXAMPLE #1 OF A SWIMMING CHECK
Kylus of the Murdock Home for Boys is fleeing the deck of a merchant ship after assassinating their captain. Sadly, he was caught on his way out and is now pursued by the crew. He jumps off the deck into the water. Farther away, at long range, his party's ship is waiting for him to get on board to set sail. After he dives, an arrow whistles by his head. He turns his head to see the crew's archers aiming at him. He has to swim as fast as she can to reach the ship before they reduce him to a drifting, bloody corpse. He decides to dive so the archers will have a harder time shooting at him.
The waters are relatively calm but there are still waves. The GM calls for an Average (dd) Athletics check. The sea is dark however, adding bb to the check. Fortunately, Kylus is a skilled swimmer and rolls ssaat.
Since the roll succeeded, Kylus can swim, treating the water as difficult terrain and thus requiring twice as many maneuvers to move. Kylus's player spends the aa to have him swim for 2 more additional rounds without having to make any more checks. Then, Kylus's player spends the t to make Kylus treat the water as normal terrain rather than difficult. It takes two maneuvers to move from long to medium range, which he accomplishes that round. On his next round, he will spent both his maneuvers to move from medium to short as the effect from the t wears off. On the third round, his maneuvers will bring him within engaged range of his ship. From that point, he would have to roll again to swim but since he's currently holding onto the ship, he will simply use a maneuver next round to climb on board and the ship will set sail away from distraught crew of the merchant vessel.

EXAMPLE #2 OF A SWIMMING CHECK
Hathom is the captain of a merchant ship. After suffering a violent storm that crashed the ship into a high reef, the ship is sinking. Hathom's only chance is to jump into the treacherous water and hope to reach the coast of the nearby island. The violent storm is making this a Daunting (dddd) Athletics check. Hathom can hold onto a large wooden plank to help keep his head out of the water so the GM adds a b to the pool. Hathom's player rolls and generates fhh, failling to swim toward the island. In addition, the GM spends the hh to have the wooden plank be pushed away and have Jacob go underwater. From that point, he has to hold his breath and will not benefit from the plank when he makes any future checks.