Must have contact with the surrounding sea, apparently. The hydrotechnicians in Colonization 212 are working over time to fix this. A new version will be ready soon. Also: better routing! No sims now get house arrest and can't get to work. And I redid the houses with custom content, so they don't have any. Add your own :) I also improved the technology for the home-greenhouses, so that they will be easier to use for actual planting. I will also post the new versions of the houses so you can replace the ones you have, if you don't care if your lake has fish.