I Need Some Advice, Please...

I've been swimming for 2 years. I'm very obese, and swimming doesn't agrivate my knees at all, all orher exercises do.

I started from scratch and can now swim 13 - 14 laps in about 23 mins, without stopping.

I try to swim atleast 4 days a week, but I normally only make it 3 days a week.

I haven't been able to lose weight with just swimming. Recently, I had someone else tell me that I'll never lose weight swimming at my speed unless I increase my swim to a full hour.

Is there anyone that knows more than me, that can either confirm or reject their assessment?

I've worked hard to get to where I currently am. Swimming for an hour straight at 350lbs is not even remotely realistic for me.

Is there a more realistic avenue to losing weightvwhile swimming.