Going to the beach with my period?

Yesterday i started my period for the first time. ( i dont know if this makes much sense, but ive had alot of experienve with spotting, so this isnt the first time this has happened, however, with the way the blood is and how it hasnt stopped yet, its gonna be a full cycle this time) so anyways, only this nasty brown stuff with these tiny clumps goes in the pad, but when i wipe its red. And, after all night, nothing went in the pad, but all came out when i wiped. My family is going to the beach today, and i dont know what to do!! I dont have swim shorts, but i do have denim shorts that i could wear. Should i wear a panty liner with my bikini bottom, a pad with undies and denim shorts, or what? Tampons are out of the question because i dont feel comfortable with them quite yet. The deepest ill go in the water is probably knee- mid thigh deep. Im 13 btw