From - The American Heritage® Book of English Usage.
A Practical and Authoritative Guide to Contemporary English. 1996.
Word Choice: New Uses, Common Confusion, and Constraints
104. dive
The kids opened the box and dove into the pizza. But should they have dived?
The verb dive has two past tenses, dived and dove, and both are acceptable. Dived is actually the earlier form, and dove may seem strange in light of the general tendencies of change in English verb forms. Old English had two classes of verbs, called strong and weak. Strong verbs formed their past tense by a change in their vowel. Thus drive (past tense drove) and fling (past tense flung) are descendants of Old English strong verbs. Weak verbs formed their past tense by adding a suffix related to -ed in Modern English. The verbs live (past tense lived) and move (past tense moved) come from Old English weak verbs. But not all of the descendants of Old English verbs have preserved this pattern. Many verbs have changed from the strong pattern to the weak one; for example, the past tense of help, formerly healp, became helped, and the past tense of step, formerly stop, became stepped. Over the years, in fact, the weak pattern has become so prevalent that we use the term regular to refer to verbs that form their past tense by the addition of -ed. However, there have occasionally been changes in the other direction. For example, the past tense of wear, now wore, was once werede; that of spit, now spat, was once spitede. The development of dove is an additional example of the small group of verbs that have swum against the historical tide.
KC_Scubabunny 
