Real Vikings pickup their ships and carry them over land

You can push a longboat as easily as a Karve. You can park either ship a couple meters from the shore and wade in to shore or if you stopped at an angle you can take a running start from a longboat, jump, and land dry footed on shore.

Once the ship stops moving it won't drift even when there are waves. A friend of mine that quit playing was sailing in his Karve and got attacked by a sea serpent. He jumped out of the boat about 50 meters from shore and tried to swim to get away from the sea serpent but got killed. Its been over 1,000 game days since he abandoned that karve and its still there floating 50 meters off shore not having drifted even a single meter from the point marked on the map.

you can always make a workbench and simply destroy the longship and rebuild it if its stuck on shallow water/land (care not to lose the nails to water depth though) which usually much faster than digging it out of the sand with the pickaxe.

Boat destruct is a mod, vanilla you'll have to chop it to destroy it.

I suggest using a Karve for exploring. When it gets stuck on something you jump out and push it off ezpz.

i think its designed like that on purpose, to troll the player. part of the difficulty