SCUBA does not have anything to do with it. You can dive without gear too - off a board, off a pier, off a dark precipice in the dead of night....
One expert's view on the past tense of the verb "to dive":
But you're right about "dived." It is the predominant (and preferred) form, while "dove," a more recent development, is still frowned upon by some usage experts. However, "dove" is no longer considered an outright error. It's become acceptable in the irregular conjugation, along the lines of "drive/drove," "speak/spoke," "fling/flung," and similar verbs (sometimes called "strong" verbs) from Old English.
In this respect, "dove" is an unusual development in English. Usually verb tenses tend to simplify and take on "-ed" endings over time (as in "dance/danced"), instead of going the other way and taking on old Anglo-Saxon endings.