Changing between intervals

When I do ows I swim in my tri suit to keep myself used to the feeling of it. If you did that, there wouldn’t be any changing necessary.

Wear a tri-suit for swimming. If it's a bit chilly out or you feel awkward riding in it in a non-race situation (I have lived in/traveled to some places where that was the case), put on a short or long-sleeved jersey over it before riding. Or you could swim in a sports bra and tri shorts, and then put on the jersey to ride.

I'm only training for fun at the moment so not too worried about getting used to the feel of a tri-suit. I like wearing a one piece swimsuit and rash vest for the swim then changing into dry underwear and cycling shorts for the ride. Thinking how to change while out in public.

Maybe a sarong or big towel or long pool cover-up with elastic at the top--put it around your neck, slip off the suit from the bottom, and put on your bike shorts underneath. Then pull up the jersey to get decent, remove towel/cover-up and put arms in. I think there are even "changing towels" marketed for this purpose. Not much of a beach girl now (the Oregon coast is freezing cold, both the water and, usually, the air; it is rare to see anyone in the water here, even in a wetsuit) but spent several years in Hawaii and SE Asia and I think I've seen a product called a changing towel (elastic at the top, big).