Providing buoyancy to a distressed victim is the key to preventing panic and any irrational actions that may endanger you.
If you do not have access to a rescue tube or rescue board, always try to offer the victim something that floats, e.g., life jacket, a life buoy, a surfboard, stand-up paddle board, kayak, bodyboard. Even the lid of an esky or a ball will help.
Providing flotation to a distressed, struggling victim interrupts the drowning process. Victims rarely drown if provided with flotation. This may remove the urgency of immediate rescue and allow you more time to plan and effect the rescue.