Is it good to swim after having DVT eight months before? I was told to walk. Pls suggest

No problem. Swimming (and exercise in general) is just fine for a DVT patient.
It's OK to be active. Having a DVT is not a contraindication to being active. Walking, swimming, and everything in between is good for you and won't have any impact on the dvt.
History of DVT. Yes, of course. This is a very good and safe form or exercise. Keep it up.