I've never been in anything smaller than a CVS but there used to be gym with free weights in the pointy(ish) bit of Ark Royal. I was King Of The Benchpress when on the crest of a wave but rather less so when just starting out of the bottom of a trough.
I once saw an Italian-made multi-gym arrangement that used the compressing of air to simulate weights. Clearly the more air compressed, the 'heavier' the weight. As this was unaffected by the 'g' loadings on a ship going up and down waves I often thought it would be a good idea to have something like that in the war canoes, rather than the 0kg one minute, 250kgs the next that seemed to loaf around the place in Ark Royal.
The worry about this obviously got to me since the only way to counter the negative impact it was having on my life was to repair to the bar, where pint lifting was far more my 'thing'.
I'm on the Shoreham and we have a very good selection of weights for a sweeper. But then again I kicked up such a fuss about the lack of fitness stuff that they had to get more kit in. It was either a choice of shoulder press a dive boat or order weights in for me so I can lift and run with. On our ship we have 3 top end cycles, 3 rowers, we had a dips/ pull-up bar made up, dumbbells and free weights.
On the topic of Pontius' zero g weightlifting, it reminds me of the canteen flat on the batch two Type 22's in 'roughers'. The deckhead was almost two decks high and if you timed your skyward Superman leap as the bows plunged, you could grab an eyebolt/lifting eye and hang from the deckhead. Time it wrong and you smashed yourself into the deckhead and if really unlucky, the ship could plunge with you and double the drop and impact of the descent. It always made me chuckle seeing matelots dangling from the deckhead laughing and screaming in fear of what they were going to break this time when they let go of the deckhead lifting eye.