In a group of paddlers, the one simple way to know that everyone has someone looking out for them and to know who you are supposed to look out for is to use the buddy system. Everyone pairs up with another paddler - each buddy looks out for their buddy. In an ideal world each pair of buddies would be evenly matched speedwise making it easier for everyone to paddle in their comfort zone and to keep pace with their buddies. But the reality is that those matches do not always occur. And the paddlers with limited amounts of experience or skill really should be buddied with better paddlers so you are much less likely to wind up with buddy pairings where both paddlers get into trouble and are unable to help their buddy. At least one paddler in each buddy pair should probably be experienced and competent in the chosen paddling conditions, otherwise it probably isn't wise for either to be on the water.