You can make your own. Using any sort of blue brush within an image editor for the water will do.
Here is where the empty map image is:
http://www.greenfoot.org/images/greeps/map-empty.jpg?1345204194
The data for each map can be found in the Earth class:
Where the first entry (for map1 - {480, 100, 0} ) contains the data for the ship (480 - vertical distance ship will move, 100 - x location, 0 - initial vertical location).
The other entries are the tomato piles (i.e. {40, 721, 532} ) where the first number is the # of tomatoes, and the other two are coordinates.
private int mapData = {
{ {480, 100, 0}, {40, 721, 532}, {12, 400, 560}, {40, 615, 400}, // map 1
{40, 642, 192}, {16, 128, 113}, {30, 400, 40} },
{ {496, 709, 0}, {10, 322, 422}, {40, 700, 241}, {40, 681, 49}, // map 2
{10, 317, 54}, {50, 90, 174}, {40, 60, 339} },
{ {272, 394, 0}, {10, 39, 30}, {30, 71, 476}, {50, 398, 520}, // map 3
{40, 655, 492} },
};
Oh also I think the image is a couple pixels short. My guess is that after you paint your water, you meant to resize it - making the edges of the water somewhat soft. Needs to be 800x600.