Margaret Avison tels the reader that "Everyone" will at some time or another face challenges, his or her own "whirlpool." Unfortunately, some people will not recognize or rise to this challenge and they will miss the "moment." Although they will not have to suffer "The black pit," they will also not benefit from "The mysterious, and more ample, further waters."
Life for people who do not take risks and who sit on "the rim of suction" may be boring, as revealed by their "bland-blank faces." She does warn, however that, unfortunately, for those who do try and who "dare the knowledge," success is not guaranteed and they may suffer " an eternal boon of privacy." No-one will ever know what they discovered during their risk-taking and their "secret" will remain theirs alone.
Avison suggests that it is worse not to have tried or be able to "even guess at the anonymous breadth" and reminds the reader that "one or two have won." She lets the reader know that the reward in striving for this goal is "The silver reaches of the estuary." The estuary represents fulfilment and is a calm and relaxing place. An estuary is a place where streams converge, and represents the ultimate goal. Estuaries contain eco-systems which are very productive and the mix of sea water and fresh water result in unique communities. Thus the reader can understand the benefits of making it all the way to the estuary.