Here is a listing of hotels near the beach in Santa Monica:
http://www.santamonica.com/where-to-stay/stay-pier/
http://www.santamonica.com/where-to-stay/stay-downtown/
In Manhattan Beach:
http://www.ci.manhattan-beach.ca.us/...anhattan-beach
Most of the larger hotels in Manhattan Beach are not right next to the ocean like Santa Monica so if you want to hear/see the ocean, you should stay at Santa Monica. But Manhattan Beach is a lot closer to South Gate for your business meeting.
I would not recommend staying further south than Manhattan Beach (e.g. Redondo Beach) because driving time to some tourist destinations (e.g. Rodeo Drive) becomes an issue. You only have 1 day so stay somewhere central.