The dive tackle pertains to swimming and suicide.

Running toward the opponent, the tackler leaves the ground when at a distance of a length and a half and dives at the runner, aiming to tackle a few inches below the hips.

A dive tackle well done always accomplishes a well-defined pause in the runner's progress.
Joel was having hard work of it.

Time and again he launched himself at the swaying legs, bringing the canvas man to earth, but always picking himself up to find the coach observing him very, very coldly, and to hear that exasperating gentleman ask sarcastically if he (Joel) thinks he is playing "squat tag." And then the dummy would swing back into place, harboring no malice or resentment for the rough handling, and Joel would take his place once more and watch the next man's attempt, finding, I fear, some consolation in the "roast" accorded to the latter.
It was toward the latter part of the second week of college.

Joel had practiced every day except Sundays, and had just arrived at the conclusion that football as played at Harwell was no relation, not even a distant cousin to the game of a similar name played at Hillton.