Painted turtles are commonly found around quiet bodies of water. These brightly colored turtles gain their name from colorful markings along the head, neck, and shell. They often can be observed basking on logs and rocks around a body of water and will quickly scoot into water if threatened or disturbed.

https://portal.ct.gov/DEEP/Wildlife/Fact-Sheets/Painted-Turtle

The turtle’s breeding season is March through mid-June, so I think maybe the turtle is out looking for a mate.