Billionaire investor Alex Waislitz has criticized a deal under which the Murdoch-owned Fox Corporation will acquire student loans start-up Credible Labs, in which he is a shareholder.

Waislitz, owns about four per cent of Credible - as well being a major partner with Antony Catalano in Australian Community Media - says Fox got a bargain.

Under the $585 million deal, Credible will be merged with a unit of Fox, which is acquiring all the shares in the company except those of founder Stephen Dash, who will retain what will become a one third per cent stake in the Fox unit.

Buying Credible will help Fox "deepen consumer relationships", Fox executive chairman and chief executive Lachlan Murdoch said.

Fox Corp's entertainment division has also agreed to acquire animation studio Bento Box Entertainment, which produces content for Fox and Netflix. Sources say the deal is worth less than $US50m, and it is the first acquisition since Fox Corp was spun off from 21st Century Fox following the latter's takeover by Disney. Bento Box will continue to produce content for other TV networks and streaming services.