Perhaps he was scared by being in just the big bath for the first time (I assume that you mean that for 14 months he has been in a baby bath in the big bath)? If so, I have a couple of suggestions (in no particular order!):
- put his playmat in the empty bath while he is fully dressed, just get him used to being there. Assuming that this works, next time try him in just a nappy and gradually work up towards being in the big bath, 1 step at a time.
- get into the bath with him in your arms and try and make it as much fun as possible (sounds daft, but getting in by yourself once or twice might make it easier when you actually get in with him!).
Good luck, I'm sure you'll succeed!!!