Marina del Rey is the southern neighboring 'town', I say town because it is an unincorporated community - meaning it doesn't have it's own jurisdictional body, of Venice and Santa Monica. You touched the beachfront/ocean activities and you'll have an array of choices of spending some pretty fun times.
1. The Venice Boardwalk. Trust me, it'll be an experience.
On a good day you can see both the planes getting off from LAX and boats, yachts, and kayaks going up and down the marina. On a cloudy day like the day I took the picture, you don't get to see much..
A very nice place to walk along the harbor and do a little souvenier shopping. There are a couple of good restaurants...one for good food and cocktails is Shanghai Reds.