Can't get into the pond

Today I walked past a pond full of goldfish and I thought it might be quite nice to jump in and have a little swim with them.  But guess what?................................

....................I couldn't jump in because I was on my lead. And even if I hadn't been on my lead, the pond was covered with netting.  Why do you think that is?.....................

Is it to stop gorgeous little collie's going for a splish, splash, splosh?  Is it to stop people stealing the fish?  Is it to stop birds eating the fish?

Who knows???!!!