The mermaids speed is now uncoupled from their faith. Before this update low faith would cause mermaids to slow down. Faith still plays an important role (abilty to regain health, power to cast spells).
I hope this change makes the game more enjoyable overall.

There are a number of reported bugs that I haven't been able to fix yet. If you see a bug report, encountered something similar and have more information, please let me know in the discussions.