Now we're talking. Finally, a teacher wants us to do something fun. Show us to the lake!
The line is a little surprising too. With our teacher-speaker, we might expect something more along the lines of: I want them to study five hours each night. Not this guy, he's all about the kicks.
Basically, this line gives the poem a sense of exhilarating fun and surprise—things you might not be used to experiencing in poems, but senses Collins wants us to be aware of when we read poetry.
across the surface of a poem
This line changes things a bit. Line 9 probably had you picturing a sunny lake scene. Now we realize the speaker wants us to waterski "across the surface of a poem." Um, okay. Will we need a life vest?
Actually, if we consider that before we were walking inside a poem, it doesn't seem soooo strange to be waterskiing across one now. The distinction between surface and interior is key here.
In the previous stanzas, the speaker wanted the readers to explore the sound and the content of the poem. Now he just wants them to kind of skim over it and enjoy what they see.
The speaker wants the readers to have fun, to enjoy what they are reading.
Don't get too deep; he doesn't want us to go scuba diving. He wants us skimming along the surface with the sun and the spray, not trapped in some deep, dark, underwater cave.
waving at the author's name on the shore.
This line assumes that we are stable enough on our waterskis that we can look up and wave to someone on the shore. The speaker wants us to wave to the author of the poem— to acknowledge the author, to know who wrote the poem.
What's important here is that the author seems kind of like an afterthought. The primary thing is that we are waterskiing. We are not asked to study the author on the shore, or write 500 words about the author on the shore. We are simply asked to acknowledge the author. Give him the hi-sign and ski on down the road (read: lake).
Also noteworthy is the fact that the author is far away, on the shore, not in the water (in the poem). In fact, we aren't even really waving at the author, we are waving "at the author's name." This is placing even more distance between the poet and the readers.
Sometimes the speaker of a poem is the poet, and sometimes the speaker is someone (or something) other than the poet, as in the case of a persona poem. The poet is a factor, but the poet is not the poem. The distance that Collins creates between the readers out on the water and the author's name on the shore emphasizes this fact—or maybe he's just saying poets aren't that fun to hang out with, so be cordial but keep your distance.