As a medic, I would encourage you to get an X-ray. You may not have broken it totally but possible cracked it, stress'd the joint, chipped your acromium arch/process or your humoral head. Either way you don't wanna wait, sooner your healed, the sooner your back in the water. Plus, what happens if you have small fracture, and complete it to full compound on the river??? ......that would suck to be your friends and for you! Play it safe!
What you describe in rotator pain does seem like it will be fixed with duck tape and bailing wire!
Hope all is well!