(try this, it's fun - and who knows, you might save a life one day)
If someone falls into a pool, it's usually more humourous than a cause for alarm. Even if they are hurt, as long as someone sees them, they can be pulled out quickly enough to prevent drowning.
If they fall from a boat, or into a fast-flowing river, it's more serious.
If someone falls off the back of a boat doing 6 knots, Instantly they are too far away to climb back. In ten seconds they are 30 metres away - too far to throw a line. In five minutes they are nearly a kilometer away, about the apparent size of the planet Venus. In 30 minutes in cold water, they may die from hypothermia.
Step 1: Equipment Required
In a real emergency, if you don't have something, improvise. It's more important to get on with the rescue than to waste time looking for the "correct" equipment.
The following items are useful, at the least. They may be required equipment in some jurisdictions and for boats of a certain size.
- 60 metres of floating line
- two life buoys, or medium sized floats
- a marker buoy
- a boarding ladder (should extend 80cm into the water)
- a sling, or harness
- davits or spar with block and winch
- floating lights
- PFD (personal flotation device or life jacket), one per person, with light and whistle
- GPS receiver
- VHF radio
- Heaving line (flaked into a soft bag for an effective throw)
- powerful flashlight or spotlight
- swim fins
The purpose of the marker pole is to be visible in waves several feet high. Typically the pole is sold with a code "O" flag ("man overboard") in a cover. Mine was lost and replaced with a scrap of fabric.
The small floating lights are suitable for attachment to a PFD. The larger one is intended to be attached to the life buoy, but may be used separately. The small ones are activated by contact with water, the larger one by orientation (when stored inverted, it is off).
The sling shown is actually intended for someone to sit in while working aloft, not as a rescue sling. But it is strong enough, and easy to secure around a victim.
A block and winch are useful to retrieve an injured or unconscious victim. On a sailboat, the main boom may be used as lifting tackle as shown. On a powerboat, a boat davit may be available. Even on a relatively small boat, the deck may be a metre above water level so a "pool rescue" technique is unsuitable.
(It would probably be better to stow the bicycle somewhere else. However, it is not actually preventing easy removal of the lifebuoys. The buoy shown needs repair, but is fully functional - anything to hand is better than the best equipment stowed out of reach)