If any creatures try to enter uninvited, these guards fight them and drive them away.

Their swords are sharp and strong, and they are fierce fighters, I assure you." "I've known 'em to attack ships, an' stick their swords right through the wood," said Cap'n Bill.
"Those belonged to the wandering tribes of swordfishes," explained the Princess.

"These, who are our servants, are too sensible and intelligent to attack ships." The band now headed into a broad passage through the "gardens," as the mermaids called these gorgeous groves, and the great swordfishes guarding the entrance made way for them to pass, afterward resuming their posts with watchful eyes.

As they slowly swam along the avenue, Trot noticed that some of the bushes seemed to have fruits growing upon them, but what these fruits might be neither she nor Cap'n Bill could guess.
The way wound here and there for some distance, till finally they came to a more open space all carpeted with sea flowers of exquisite colorings.

Although Trot did not know it, these flowers resembled the rare orchids of earth in their fanciful shapes and marvelous hues.