Well, the lanes are for people who want to do lengths (lengths of the pool). :)
It varies in competition. In many pools lane lines will have around six feet between lane lines, while in bigger pools used for higher levels of competition the distance can be 8 feet or more. FINA requires that lanes be 2.5 meters wide for the Olympics and international championships.
It depends one what pool you go to. There are some swimming pools that have lines on the bottom and there are others that do not
It depends on the pool. Most competitive swim meets take place in 8-lane or 10-lane pools. Meets taking place in 10-lane pools typically fill the entire pool for the preliminary heats. In other words, all 10 lanes are taken up by swimmers. However, in the semi-finals and finals, only 8 lanes are used. This keeps the two outside lanes empty. However, meets can take place in pools of any size. There can be 6-lane pools or 4-lane pools. It is not always the same.
when people swimming lanes divided by lane lines
that would depend upon the length of the pool. The Most common lap pools in the USA are 25 yards. Some are 25 Meters. If you have an Olympic size pool they could be 50 or even 100 Meters or yards. Most of the lane lines are about 4 inches wide.
Double yellow continuous lines means stay in your lane, which is the right hand lane on a 2-lane road in the United States. You are not permitted to cross double yellow continuous lines. In some jurisdictions, the police will ticket you if your tire even comes close to or touches the double yellow lines because you are encroaching on the opposite lane's space.
As far as I know, regulation dimensions for a short course pool is 8 lanes wide by 25 yards long. Long course pools are 8 lanes wide by 50 meters long. However, I have seen a lot of competitions in 6-lane pools, and some in 10- or 12-lane pools. One time, I went to a swim meet in a 4-lane, 20-yard pool, but that was pushing the limit.
In Olympic swimming pools there must always be 10 lanes. Although only 8 of these are used it still must have a lane rope between each lane, so there are 9 lane ropes used.
The lane lines will disappear AND/OR there will be a caution sign advising you to merge.
They mark the edge of the carriageway/roadway.
The lane is between the lines of the paint (the lines where the players line up rebound a foul shot) all the way down the court.
Lane lines are made of lightweight materials that will also float on water. Common materials include ropes with plastic buoys or thin metal cables with buoyant plastic rings on them.