It's natural to move towards Jyn the moment he realizes she's coming in for Luna; they've been a partnership for longer than they've been parents, they're always in tune with one another that way. Once he realizes his father's hands are free, Mateo lets go of the shorts and reaches for Cassian's hand, still pouting. With his now free hand, Cassian runs his fingers through his son's messy hair and then ducks down to be more eye level.

The water is deep to Mateo, but even kneeling it barely brushes Cassian's stomach. "I will be right here. Maybe we can break your last record. And then maybe in a few minutes, we can go out a little further?"

He'll carry him, of course. Mateo does not like not having his arms around someone's neck when his little feet can't touch the sand.

Slowly, tentatively, Mateo nods his head, still looking like a grumpy octopus. It is the exact same unhappy frown Jyn gets when she's grumpy. "But I don't wanna be Luna's partner right now. She hurt me."

"You do not have to be," Cassian says gently, still trying to head off those wails. "It is okay to be upset. Just because Luna is too little to understand what she has done is wrong, it does not mean you need to ignore that she hurt you and hurt your feelings. She is still learning all the things you have gotten so good at."

"Okay." He pauses for a long five seconds, then looks over at Jyn. "Mama, will you keep Luna over there?"