Joining the Navy but need help about my asvab and job searching!!!!?

I have been talking with a navy recruiter about joining. I just took my asvab and got a low score of 48. My recruiter keeps telling me to do this seamen apprenticeship/ undesignated seaman. I heard that you DONT want to do that and heard dont sign nothing until you find a job that is open you want. I would love to do something in aviation, specifically a aviation electrician but wouldnt mind any similar jobs. I mentioned to my recruiter that what if i didnt want to go undesignated and he didnt like that. Should i risk retaking the asvab for a better score? or should i not sign anything at meps until a job im interested in opens up? I just dont want to get screwed over :/