MY ANSWER IS:

1.Star + fish -> Starfish.

2.Sea + horse -> Seahorse.

3.Ship + wreck ->Shipwreck.

4.Drift + wood ->Driftwood.

5.Sea + bed -> Seabed.

6.Jelly + fish -> Jellyfish.

7.Sea + weed -> Seaweed.

8.Under + water -> Underwater.

9.Sea + shell -> Seashell.

10.Sting + ray -> Stingray.