Hey, i need help to make a random encounter table for 5e. This

File: stranded at the sea.jpg (53KB, 700x394px) Image search: [Google]

53KB, 700x394px

Hey, i need help to make a random encounter table for 5e.
This is the situation: i'm running a campaign with a paladin, a cleric, and rogue. The cleric and the paladin are agents of the goddes of water, and the rogue is sticking with them because he owes some money to a bunch of different gangsters and he needed protection. At some point he commited a crime against the party, so he was sent to trial before the temple, and after being found guilty he had two options: one, to swear total loyalty to the service of the goddess (sticking with the party). Or two, facing the judgment of the goddess directly (that is, being thrown at the sea).
So, i need ideas about how to execute the second option; my obvious idea was to make a random encounter table, with sharks, dolphins, etc. which i would roll every 5 miles (and he is going to get thrown around 15 miles from shore), and make him roll some constitution saving throws to see if he gains points of exhaustion.
So, /tg/, how can i make this interesting? How much does he has to roll? Do you have any other better idea? How difficult should it be? Remember that it has to be funny, probably not many people can swim that far but i don't want it to be a definitve death for him.