1.after retiring
->after retiring,my uncle-a lover of the sea-took up a strange leisure acrivity
2.he goes to the beach in the morning
->he spend most mornings at the beach
3.the sea is vast and quiet
->...and enjoy the vastness and quietness of the sea
->tobe+adj
4.yes,they can
->many of the things i pick up from the beach are still useful to someone...