Back cramp after wet suit swim

Just curious if anybody else has experienced this. After the swim and once on the bike my lower back really cramps up. I don't have this issue on a normal training ride. I did a HIM this weekend and getting out of the water my hamstrings were really tight. Then once on the bike my lower back was really tight. Same thing has happened in the past and only when wearing a wet suit. Is it possibly to have too much buoncy in the legs of a wet suit? I seems that maybe my legs are being lifted too high causing fatigue in my lower back. Maybe need to improve flexibility or strength? Any suggestions?