The cops wouldn't be wasting time with divers and shooters for no reason and there was a good lead for them to go to that extent. IMO
What made the cops search that lake?
1) Someone saw something or dobbed.
2) Either Toyah's or the suspect's phone pinged there when they've said they were elsewhere.
3) Clothing or items were floating or washed up.
For example, the guys who followed the murder of Karen Ristevski saw the cops searching fields, dams and bushland many kilometers away for, it seemed at the time, no rhyme or reason but what we didn't know is that the cops were following both the phone pings of the victim and the murderer in that area at the time the murderer said he wasn't there.
The cops have to sift through everything from dashcam footages to crazy psychic nutters.
They have to be 100% sure with evidence before an arrest.
I trust our cops.