Yoko, Will You Do Me a Favor? Episode 12

The Great Gurren Brigade are now on their way to Beastmen's capital city, Teppelin but there's a vast ocean in there way. The only way for them to get across is for the Dai-Gurren to be modified, so while they wait everyone goes to chill out at the beach. Once preparations are complete, the Great Gurren Brigade begins their cruise but there's an ambush waiting for them.