He looks identical to his son, as he wears a brown shirt. The only differences between him and Squidward are that his shirt is a lighter shade of brown and he wears a red tie and glasses.
He is mentioned in "Krab Borg" when SpongeBob tells Mr. Krabs that Squidward's father never hugged him. Squidward then claims that his father loved him very much.
Jeff Tentacles makes his physical debut appearance in the book Hooray for Dads!, indicating he is alive, contrary to what the past tense used when referring to him in "Krab Borg" may indicate. It is possible Squidward was referring to his time as a child, rather than meaning that his father was deceased.
Mr. Tentacles is shown to have a similar personality to his son as both have an uninterested air to them. He seems to care for his son as he was willing to spend time with him for the events.