There are two ways to tell if the timing belt has been replaced. One is obvious-you are looking at a service receipt showing the replacement.
Swimlane diagrams are used whenever you need to show activities, tasks, or process steps which are being performed by different actors/roles. You can use swimlanes to group activities in an activity diagram or process flow by any category what you need: by role, by system, by department, etc.
The swimsuits used in competitive sports are designed to reduce water resistance or drag on the swimmers as they push forward in the water. The drag faced by the swimmer in the water is caused by the body shape of the swimmer and the friction of the water against the skin of the swimmer.