From StrategyWiki, the free strategy guide and walkthrough wiki

Prerequisites
Mission: Life's a Beach Location: Burger Shot car park, Marina, Los Santos

This is your introduction to stealth missions and there's really no need for a walkthrough. The basics of it all is to crouch and kill the guards with your knife. If one of them is alerted, it's okay, you just have to knife them all out of your way. Once you get the rhyme book, you could sneak out or shoot your way through.

[edit] Rewards

• Respect: +4
• Item: Knife