letting me go to the beach with my boyfriend

Til

okay so i’ll be 18 in june and my boyfriend along with our friends (they’re a couple too) wanna go to the beach. for 2 nights and 3 days. i don’t know he to tell my dad. he’s protective over me, my mom would be okay with it. i’m about to leave for the navy in august and i just want to hangout at the beach with my boyfriend and or friends. any advice?