Oh I saw that whale the other day, but can't think where, sorry! Unhelpful
We have got a great bath toy which swims and sings, I haven't got the packaging any more, will see if I can find out what it was called.
OK found it, it hasn't got very good reviews though, we have not replaced the batteries yet (it doesn't need the batteries to swim, only to sing) - TBH the singing isn't that important - it's only impressive out of the bath, it hums when one way up and then when you turn it over it gargles without starting the song again which is really clever. You can't really hear it singing when it's in the bath though. Also it swims backwards when on its front and forwards on its back, which should probably be the other way around. But it does swim very well.
Yes it has a little knob on its back. It's quite hard to wind but easier if you just rotate the arms backwards and let them go. It's quite big though - would be ok with one child in a bath but with 2 children/one adult it would probably get stuck.