Triathlon on my way, maybe?

Went to the Y today, primarily to swim. My daughter came with today, and my wife was out with her family. After about a hour in the pool doing mostly drills, and trying to swim front crawl, which I actually managed for a few laps. I got out of the pool, showered up quickly and went to find my daughter. She was reading as usual, and I messages my wife. She wasn't back yet, and my daughter wanted to finish the last chapter of her book, so I figured I might as well walk a bit whilst I was waiting. I figure I must have swam about 1500 yards, and ended up walking just shy of 4km, so a pretty workout all in all. I guess all I'd have to do is spend about 30-40m on a bike at a good intensity, and that'd not be a stone's throw away from a mini triathlon! I know I used to fairly easily hit 18mph on a bike, event when I was bigger, and faster when I I was in shape by a good bit. Used to do a 30 mile ride with the bike club in the UK every week, and it was in the evening so I couldn't have been more than two hours, and I know we used to move at good clip, easily 24mph in a pack on e level. I certainly felt I could have done another half hour of something, I wasn't particularly out of breath after walking. In fact it's one reason I don't prefer to walk that much anymore, I'd run if I could, but my knee still won't take it.