Can an owner of property be held liable for a death where one died by drowning in a swimming pool?

Maybe. But be prepared to show how the property owner was negligent. An property owner is responsible to his guests or invitees to have reasonably safe conditions on his property. To win your case, there would have to be an unsafe condition at the pool that the owner should have known about or did know about, and failed to fix the condition in a reasonable time. If you claim that there was inadequate supervision, you must show how other property owners have more supervision, have an expert in pool safety testify about the proper supervision for swimming pools, etc. Since negligence is hard to prove, you should see a personal injury lawyer right away (most give "free consultations" and you don't pay unless they win--see the phone book).