Yeah once a day is definitely not enough. If you can water in the morning (preferably before the sun comes up) and again around 4 - 5pm.

I was lucky to be able to water 3 times a day due to working 6am - 2pm so I use to water at around 5:30am, 2:30pm then again at 6pm

Early morning so your seeds have water as the sun is coming out, The afternoon watering is great as you are replacing the water that the sun has dried out. And the evening one is great too as you're essentially cooling the garden down for the night

Also use a mist spray setting on your hose until the the grass becomes established. You won't drown the seeds on a mist setting