Most of our paintings here contain water whether it be seascapes, lakes, rivers, streams or even tiny puddles. I always feel that waterlines are their crowning glory. But sometimes they just don't look right and there's nothing worse than feeling like you've messed up at the last minute. Firstly you will have to decide why they don't look right. It could be that they're not quite straight, it could be because too much paint on the knife makes the waterlines too thick. Try to make the waterlines in the distance thinner than the ones in foreground, hardly noticeable, you want them to look further away, you just need a very small amount of paint on the knife, and if any of your waterlines are a bit on the thick side when you apply them go back in with a clean knife and rub over the bottom edge until it fades away to the degree of thickness you want it. If you're not happy with the result use a brush to blend the whole waterline into the background then re-apply. I often forget how great this wet on wet technique is for allowing us to make changes.