Get dirt and sediment out of your swim top by removing as much of the grunge as possible before you launder it. Soaking also helps to remove lake water grunge from swimwear.
Prepare and de-grunge the swim top
Start out by shaking or brushing loose any dirt or mud from the garment. Rinse it well with cold water. With the lake sediment removed, the suit is ready for a powerful presoak.
Create a presoak mix
Clorox recommends soaking in the soiled suit in a mixture of water and powdered detergent for at least one hour. Tide suggests using a presoak solution consisting of half the normal amount of detergent used in a heavy wash cycle mixed with 1 gallon of cold water in a bucket. Weigh the swimsuit down with a plain white towel to keep it submerged in the solution.
Wash, rinse and repeat
After removing it from the soak, wash the swimwear as usual using a color-safe bleach. Do not let the suit dry until the entire stain has vanished. If the stain is still present, repeat the process until the stain is gone before allowing the item to dry. You may want to use an oxidizer at this stage as well, especially if the stain has had a chance to set.