I had a similar experience my my old boat which had a Alpha gen one. Had a bad gimbal bearing, pulled drive (first time for me) and found small amount of water in bellows. Could not find a leak or tear in bellows. Put drive back in of course was too green to glue in big ring gasket. Put drive back on after doing gimbal, next time I pulled the drive there was no water in there- had no issue with u joints ... Now with more experience thinking maybe the shift shaft seal but who knows.
Big issue is if you get a lot of water in there and never take the drive off, Input yoke will rust and mess up seal. On the older drives with out the lube bottle if you don't watch your level, the gear oil leaks into bellows until upper runs dry...