One does fit.

I finally drop my shorts with my cock just sticking out as it's too short to hang, she looks at me critically and grabs a pair. I put them on, and they fit at the waist but are loose in the front; five pairs later and these fit like a glove with a bump around my dick. They feel so nice and strange. I get hard, and the material stretches out as I rise and it shrink-wraps around my dick.

"Finally a fit." Rose says. "Now to the next stage."

I ask. "What's the next stage?"

Rose doesn't answer, opens the door and shouts "Mom!" A minute later Susan turns up.

"You look so cute sweetie." Susan said tousling my hair. "Of course, back in my day, all the boys swam naked... Pity they stopped doing it."

"What!" Both I and Rose say.

"Yes." Susan says. "Girls in a one peace and the boys naked and unashamed, even at the beach."

After hearing this, Rose, with some difficulty, takes off my speedo and now I'M naked with a boner.

"Cool!" Rose says. "Let's start in my garden pool. You could do with a tan."

Rose gathers all my clothes and puts them into the laundry basket and hands it to Susan.

"Can you do these now, Mom?" Rose says.

Susan nods and smiles. Rose grabs my hand and drags me out and down the stairs to the pool.