I was in a bathtub with my boyfriend and he ejaculated into the water. then he fingered me if the water with the sperm in it got into my vagina could it cause pregnancy?

Yes: There have been reports of pregnancy from similar circumstance, but odds are really not in favor of pregnancy. Of greater concern is that you put yourselves into a position of unwanted pregnancy like this. Please get education for both you and your boyfriend regarding prevention techniques which may include pills, diaphragms, spermicidal gels, condoms, implants and social distance, among others.