Hi I'm a scuba diver and will try to answer your question. For the past 2 years we've flown a charter called Sunwing where we were each allowed a 44lb suitcase and then a 2nd dive or sports bag for another 44lbs. It was great.
This past September we went to CN for the first time and were flying on Air Canada points. But we were only allowed one suitcase weighing 50lbs. OMG how is this going to work??? Our dive bags are 44 lbs each. Well it turned out we were under utilizing our carry-on. We use to call our carry-on our knapsacks that had our prescription masks, dive computer, camera, etc. and our one personal item was my purse and hubby's netbook. I was in a panic until I realized we could each have a 21" pully bag as our carry-on and our knapsacks as our personal item. Of course purse & netbook had to go into the bags but this was doable.
I've always been surprised by people who can carry enough clothes in their carry-on. Well we did it. Only had to put our toiletries in the dive bags which were being checked.
I know Couples supplies all the scuba gear but we like our own and now that we've got it worked out it's going to be our set-up for Cozumel in January and then CN in May and again in September. And believe it or not I did have 2 pairs of shorts that I never wore.
Hope this helps
Couples Negril - September 2011, 2012, 2013 and have just booked 2014
Scuba Club Cozumel - Jan, Apr & Nov 2012 and Jan & Nov 2013
Cobalt Coast, Grand Cayman - May 2013
Retiring & moving to Cozumel, Mexico in early 2014