Hi. Well, I'm wondering if your son does not like the water on his skin. I know he takes showers and such at home but . . . the way the nervous system can work if sensory issues are at play is that things/feelings are intensified in different enviroments. If you are at a pool for example, you have kids screaming, water splashing, an element that feels slightly out of control to a 5 year old so . . . his system is revved up. Then . . . the water feels uncomfortable to him. My son had issues with his hands getting wet in preschool for example to the point that he'd have a tantrum about washing his hands. AT home, he didn't. It creates a "flight or fight" response which is base level reactions to stimulus that the nervous system finds unacceptable.
My son does not wear shoes at home . .. ever. In the middle of winter, no shoes, no socks . . . barefoot. We have a rule that he wears shoes/socks when he leaves the house or if he is at someone else's house . . .but at home, they are off immediately. Your son leaving them on may be that he doesn't want to change sensations on his feet in a new place perhaps.
So, I'm left wondering about tactile defensiveness with your son. An occupational therapist addresses this and I will tell you the water issue got better really quickly for my son.
What I would do is NOT push him. I'd put the bathing suit in your bag or his and tell him it is there if he changes his mind. Let him play in the sand on the beach and if he gets hot----- he might start walking in the water. Then he might want to put his suit on.
I would try not to let him sense your concern or worry and see what happens. My son started going off the high dive when he saw his friends doing it but if I had asked, he'd run the other way.
Good luck
Tixhe has some good points. Especially when she says, "i just gave up and let him get comfortalbe on his own." The getting comfortable was the key.
I spent about 7 or 8 years as a swim instructor (a long, long time ago) . I had kids that were scared to death of the water (and I had the scratch marks to prove it). I was able to teach all of them to swim. It took time and very slow steps. If you can find a private swim instructor that will work only with your child or maybe two others - and is willing to take the time. You can get over this fear. If you are willing to spend the time to VERY GRADUALLY introduce to fun in water on a very hot day, you also can do it. Never, ever force the issue.
As for the shoes - I have no clue!
well to address your water issue...my 3yr old son was scared of the water also. Bath time anywhere but home is still an issue sometime, but i guess thats just because he's used to our routine at home. However at the beach he wouldnt even get near the water or even try to touch the sand. And the more i forced him to try to like it, the less interested and more scared he got.Until recently when i just gave up and let him get comfortalbe on his own, the ocean water he still wont go it stays just were the waves will splash at his feet. He says "no the waves are too big" and today he actually sat in the water with me. But i guess you just have to let him come to it on his own. Because the more you try to make him like it, the faster you will push him away. But think of it as him being cautious. One old lady said to me "i like how your son knows to run away from the waves, he knows how to protect himself" But as a mother watching all the other kids enjoy the water you want your child to be part of that also...but dont worry i think its just a phase..it'll pass by.