The greater the length, the less likely water will splash in, but also the greater the dead air space. It is clear that size and shape are trade-offs and need to be considered in light of the other features. However, these valves may not work well for free divers who clear as they surface. Reservoirs Reservoirs are actually sumps or traps to hold that little bit of water that did not clear or splashed back in. Reservoirs add to the bulk and complexity of a snorkel because they need to be fairly large to be useful.
Reservoirs only work if they are combined with a purge at the lowest point to act as a drain.
Snorkels with flexible tubing tend to snag less often on other hoses or gear because they drop out of the way when not in use. Flexible tubing does increase the cost and complexity of a snorkel. For years it has been held that if a corrugated hose is used, it must be smooth on the inside or breathing resistance and difficulty of clearing would increase. We could find no such problems on these snorkels. These are a modern and far more sophisticated version of the old classic ping-pong ball closure at or near the end of a curved hard plastic top.