A - Anemone
B - Barnacle
C - Coral
D - Dolphin
E - Eel
F - Fish
G - Goby
H - Harbor
I - Island
J - Jellyfish
K - Kelp
L - Lobster
M - Manatee
N - Nudibranch
O - Octopus
P - Pearl
Q - Quillfish (a type of fish)
R - Reef
S - Shark
T - Tide
U - Underwater
V - Vulture (some seabirds are called sea vultures)
W - Whale
X - Xiphias (swordfish)
Y - Yacht
Z - Zooxanthellae (algae that live in coral)
This is just one example, and you can definitely create your own! Be creative and have fun with it!