Not if you are a UK citizen, not sure for other nationalities. You will need a Marine Park permit if you intend to dive in area out by Ras Mohammed, but that can be bought at the airport
I went there just recently and yes you do need a visa. You can either get one at the Embassy before you go or at the airport when you arrive but they will not let you through customs withouth the visa stamp in your passport. Cant rember how much but not a lot, also its cheaper in Egypt but you may get some hassel at the airport getting it sorted.