Steps To Reproduce:

1. Create an old world;
2. Go to the south/east corners and enter water (if there isn't any, make a little pool);
3. Without flying, try to leave water.

Expected Results:
You are able to leave water.

Observed Results:
You can't leave water without draining it or flying.

Additional Notes:
This happens in any area under 16 blocks far from the border, only at south and east.