After seeing the recent devlog for the 1.20 release, I was thinking the exact same thing!
I'm very excited about the idea of sailing, but it's not very practical with the current word generation (default options are 0% ocean, and oceans aren't very useful to the player currently). There should be an incentive to make a sailboat, and making a grand journey in search of resources/lore sounds like a great idea, and would be very fun. Having islands and continents with unique characteristics (i.e. unique locations/lore, exclusive end-game resources, higher probability to find precious metals, unique plants/animals) would be a nice way to incentivise exploration.
I don't know about reducing hunger when sailing, but maybe temporal stability could be reduced when in the ocean outside of a sailboat, or have sea monsters that attack you when swimming or on a raft.
Also ocean fishing could be a way of getting large amounts of fish, like tuna, but would need a lot of time to find and travel to them.
