How long to heal broken forearm, and get back to swimming again?

About 6 weeks. Most fractures will heal in about 6 weeks. This type of fracture often requires a cast or other form of immobilization. There are some water proof cast materials, so you may be able to convince your orthopaedic surgeon to allow you to swim. Otherwise, you will likely need to wait until the cast comes out to resume swimming. It should be ok to participate in running, biking and other exercises.
Depends. Broken forearm bones take 4-6 weeks to heal, depending on bone involved, location of fracture, amount of displacement and instability of the fracture, and treatment rendered. My patients treated by cast only for straightforward fractures are started in therapy after 4 weeks. I allow them to swim at that time. It really depends on your doctor and their comfort level. Full recovery in 4-6 months.