Sometimes, we can not have everything we want. Life has a way of throwing us curve balls. That however should not ever stop us from our goals. If on a given day you can not swim, row. If you can not row, run or ride then do spinning. There is always walking and walking on the sand is a little more challenging. Where there is a will there is a way. I have observed people who must use a wheel chair to get around do more in gyms than some of us who can walk more readily. Find an activity you like doing and do it. Your health will improve and You will feel better for it. Aim for at least 30 minutes five times per week.