Walking a large breed puppy Questions

Hello! Have a quick question, it’s been a while since I have had a large breed puppy. He will be fully vaccinated soon, and is very high energy. For the most part he runs around and play with my other dogs all day, but I’d love to take him on walks. How long can we walk for? Do I just take signs from him for when he tires? What’s the rule of thumb? Don’t want to hurt him cause I know he is growing fast but like I said HIgh energy lol. Any tips appreciated, thank you.

Also wanted to ask, what about swimming? If he likes it can he swim? Supervised with me of course. I have a fence around my pool currently so I’m the summer I’ll be taking it down, need to teach him about where the steps are etc, but thinking he might enjoy that.

Rule of thumb is 5 minutes for each month of age. Free running doesn't count, unless it is excessively zoomy!
I'm sure he would love to swim. Merry only paddles, but Eddie has enjoyed a swim from being a youngster. I'm not sure when he started - about 6 - 12 months I think. I would call him back to me if he was going too far out, or too near patches of weed. We don't have the luxury of a pool, we use a disused reservoir!

I kept a close eye on mine and adjusted exercise based on how they were feeling, I let them set the pace with plenty of rest stops, for me it was more to let them explore things around them than actual exercise.
No forced exercise, natural surfaces are best and hard surfaces should be avoided, until older.Yes swimming would be fine.