Pontoon Drain plugs advice?

Have a 2023 Suntracker party barge. Bought for boating with grandkids. One parent's job is making them move out of state, so I guess I will sell it. There is water in the pontoons, but no water drain plugs. Is this something a mobile mechanic can install? Also, IDK how the water is getting in. Does that normally happen? If not, can a movile mechanic determine / repair leak source? Or should I bite the bullet and go to a marine shop? Hampton Roads area of VA.