I completed the 100 miles by swimming.
It took me 86 days of actual swimming, 89 calendar days, 176,970 yards, 79.6 hours.
I hope to do the same in the second challenge. I may try to add 100 miles of rolling my manual wheelchair. That would be back and forth to the pool each day. (Well, maybe 25 miles.)
Time is the teller of all stories!