A few others I don't think have been mentioned yet:
Bridge 'The Sea'
Elgar 'Sea Pictures'
Rubenstein Symphony No 2 'Ocean'
Ravel 'Une Barque sur l'Ocean'
Bax 'On the Sea-Shore'
Bantock Hebridean Sea Poems (Caristiona, The Sea Reivers)
Bantock Hebridean Symphony
Flagello 'Sea Cliffs'
MacDowell 'Sea Pieces'
Hanson Symphony No 7 'A Sea Symphony'
and of course:
Mendelssohn's Hebrides Overture
Beethoven 'Calm Sea and Prosperous Voyage'
Bridge 'The Sea'
Elgar 'Sea Pictures'
Rubenstein Symphony No 2 'Ocean'
Ravel 'Une Barque sur l'Ocean'
Bax 'On the Sea-Shore'
Bantock Hebridean Sea Poems (Caristiona, The Sea Reivers)
Bantock Hebridean Symphony
Flagello 'Sea Cliffs'
MacDowell 'Sea Pieces'
Hanson Symphony No 7 'A Sea Symphony'
and of course:
Mendelssohn's Hebrides Overture
Beethoven 'Calm Sea and Prosperous Voyage'