First off I have no idea why it would say FeralHeart.exe so I'm just going to assume that was a typo created by distraction and you meant Last Moon.
Secondly, to fix the issue, go onto your game files and delete the "savepoint" file. You will spawn in another map. Just avoid Underwater World altogether, since the map is currently broken.
(also, please remember to always check old posts that might be related to your problems since they may contain the answer, instead of making a thread right away. This issue has been discussed in over 5 threads at this point)
