As a kid, it was hard to keep me out of a pool, but now as an adult I’m less and less inclined to go for a swim.

I was thinking about this on a cruise aboard the Viking Star, the new ship from Viking Cruises, which has three pools. The main pool is midship; there is an infinity pool aft and a counter-current pool in the ship’s spa.

I can’t vouch for the third pool, but the other two did not get a lot of use that I could see. Several passengers I talked to agreed, and they had a variety of theories about why.

One was the cool April temperatures, in the 50s for the most part. The Mediterranean will heat up as summer arrives, and that alone might spur more use of the outdoor pools.

Another factor, one older woman confessed, is that she wasn’t too happy with her appearance in a bathing suit. A man said that the pools are overflow dining areas, and the presence of diners inhibited people from swimming.

Unmentioned, but undoubtedly a factor, is that Viking does not encourage children as passengers. The 633 guests on my 10-day cruise between Istanbul and Venice were mainly in their 60s and 70s.

I have to think a ship operated by Carnival Cruise Line or Royal Caribbean International in the same timeframe and location would have more pool users based on demographics.

Which leads to the interesting decision by two cruise lines to get rid of swimming pools. Crystal Cruises planked over one of two pools on the Crystal Serenity in favor of a new dining area. And Windstar Cruises recently announced that it will remove the pool on the three ships it is acquiring from Seabourn, also for expanded restaurant space.

No one uses the pool, Windstar CEO Hans Birkholz said bluntly, in announcing the change at Cruise Shipping Miami in March.

It is tempting to think there will always be a pool on cruise ships. Windstar is adding a counter-current pool for exercise even as it eliminates the more traditional pool area.

Viking, which has no pools on its river cruise ships, opted for two outdoor pools on the 930-passenger Viking Star. And on large, activity-jammed ships in the contemporary segment, pools are an integral part of their appeal.

But on smaller ships that cater to mainly to older guests, there’s already been some erosion of the pool’s primacy. It leads me to wonder how much further the trend might go.