I'd be tempted to leave it for a little while, maybe another month or so, or until you go to Center Parcs.
We took DS1 to Cornwall when he was 2 (were there for his birthday) he COMPLETELY freaked out about the sand, even walking on it with shoes on was out of the question. We didn't go to a beach again until he was nearly 3 (we live in Wellingborough so beaches aren't exactly close LOL). He freaked out again - but this time it was because we had to LEAVE the beach - he loved it so much!!!
I would say keep at it. Both mine love swimming and I've not had a problem but I am also a childminder and one little boy I looked after was initially very anxious. He came to us at about 20 months and when he was about 26 months in the summer we started to take him swimming with us. I had him fulltime so it was difficult to go at a time when he wasn't there. He had never been in a pool before and the first time we went in clung to me and whimpered for about 20 mins until i took him out. However the next time after 10 mins he stopped moaning and actually patted the water a couple of times. Over the next few sessions he gradually became more and more confident in the water. He has never been quite as relaxed and happy in the water as my children but i am glad I perservered with it. Good luck.
DS went at the age of 4 months. Then I went back to work so it stopped at about 1.5 years. Then I took him back at just turned 3.
He was fine on the first lesson...until he fell underwater. After that, he just wanted to do his own thing, wander aorund the pool, climb in and out when he wanted.
As the lessons were structured, I was spending each half hour, trying to get him to come in and do what the other kids were doing. Anyway, after 4 lessons, we stopped going and he was not bothered on the slightest. He is starting a 'freestyle' weekly session with his dad in Spring.
As long as baby is confident in the water then being able to 'swim' as such is no big deal yet (says she who can't swim very well at all )
I'd say persevere. We took our DD at 5 weeks old and then at 3 months old on holiday but she was too young to understand. We took her on holiday again at 13 months and it took her 3 days from being clingy to jumping in on her own (with armbands of course!) Every child can be clingy in different situations but once they understand how good it is, they're fine. I would take her once a week until she gets it even if you're only in for 10mins at a time.
Our daughter was never really into swimming - especially if the pool was busy and the elder kids were slashing / shouting etc. Then we took her after not having gone for a couple of months and she started to like it. The next time she absolutely loved it and we haven't looked back.
So I'd leave it a while if I were you. The CentreParks trip is probably a good idea...