Follow these steps

open the dev cosole using F5 (if consol doesn't open look up how to enable it)

type the following
devcommands
god
fly
close the consol

you can now fly to and off the side of the world without dying.

once clear of the water at the edge of the world use crtl key to go down until you reach
the bottom. Note there is a strong constant force pushing you away from the edge so be ready to compensate for it.

find your grave marker and can recover your items

return to your base and use hte dev consone again to turn off your fly and god status. The god status will also clear if you just log out

enjoy the rest of your game :)