When he picks her up for the trip, she literally jumps onto his bike.
He strips down to his boxers.
She can feel him react to her and this causes her breath to quicken even more.
She catches him eyeing her in her bathing suit; she walks in on him changing and finds herself lingering a little; when she goes to change for bed, she discovers that her luggage has disappeared.
Then, the ultimate coincidence is revealed: Uncle Joe only has one bed.
He shifts towards her, his cock resting on her thigh.