How do self-sealing water balloons work?

Self-sealing water balloons work by attaching a set of balloons to a garden hose, which provides the necessary water pressure to fill them^[4][5]. As the balloons fill with water, they automatically drop off the hose attachment when they reach the appropriate size^[5]. While some users have attempted to fill them using a kitchen sink, it is not recommended as a long-term solution because it requires holding the balloons very tightly to the faucet and lacks the consistent pressure provided by a hose^[4].