Killa whale !! Must've gotten onto your

mrs secret spots!!  

 never heard them called cubs before   Anyway, young whales (humpbacks, at least) do not leave the immediate vicinity of their mothers. They cannot survive without them. They are never aggressive, they can be inquisitive, but, again, always under the watchful eye of mother. Did it look like a humpback? i'd say a humpback calf in Perth metro waters at this time of year would be very unusual--they were all still heading north at Ningaloo when I left there a week ago. Normally wouldn't see calves down around Perth until late September, IMO. Other possibility would be a pilot whale ( or false killer whale, so named because of their size and some light marking underneath) Or another of the smaller species, perhaps a Bruyders? Orcas are generally not solitary, and they are not aggressive towards humans at all.

If it was a young humpback, it may have been trying to just latch onto another creature for comfort? Anyway, it won't survive long without it's mother.  Adult whales can show warning behaviour if they feel threatened, usually showing their tail. We were trolling out in around 150 metres last week up there when there was suddenly a massive tail slap very close to the boat--no other whales around, so not part of mating display. We veered away, and he followed passing DIRECTLY  under us in clear sight. Our billfish trolling speed is faster than their normal travel speed , and I suppose we had just unwittingly snuck up on him/her on a parallel path. Another time, we were anchored out a bit in a fresh easterly, and a mother and calf were nearby--she stuck her tail clear out of the water and just hung there, for at least a minute. We just sat put, and they eventually moved away. I've had mothers seem to bring their calves over close to the boat--learning experience? Always be extremely careful around them. 

 Thanks for the right up yeah i ddint know what to call them so i have now changed the post to calves haha and yeah not sure if mum was around somewhere but it could of just been curious but it came for the boat pretty quick hahaha and yeah did look like a hump back but not 100 percent sure 

 could have been a minky. have heard of them being off our coast.they are of a similar size to a calf 

I've had the young whales swim right up and under the boat - seemed to be just inquisitive/playing. Each time the mum just sat off about 50-100m away and seemed happy to let the young one check us out. Never had any dramas with them though. this being off Mindarie - though didn't see as many whales around last year.
I was once told that if the whales are hanging around a bit close for comfort - to turn off your sounder as they may be attracted to the sonar from the sounder (kinda made sense - but may need others thoughts on this to verify).
Have nearly run into a few biggies at the Montes - you really have to keep your eye out for them up that way at certain times of the year.

According to the DPAW website Minke whales grow to about 8m and are known to be inquisitive. There are generally found alone or in groups of 2 or 3. We have had what I think was a Minke swimming around under under the boat for about 10 mins a couple of years back out in the 40's. 

 For the minke just googled a minke whale and looks identical to the one yesterday cheers fellas