Wear longer shorts and/or swim trunks and a t-shirt; if you have the option wear those that are big enough to cover the prescribed areas. If you do not have that option, you have a choice to make to either participate and wear what is allowed, or not participate for reasons of religious observance.

There are all sorts of styles and sizes and lengths of clothing available, surely something can be found to suit any requirements necessary.

As far as being with other men, maintaining satar is still the minimum- of course you'd dress more modestly in the presence of women.