The Sea Monkees' Castle
From A KoL Wiki

desc none rect 195 279 294 378 Grandma rect 54 397 153 496 Little Brother rect 231 397 330 496 Big Brother rect 95 279 194 378 Grandpa </imagemap>
The Sea Monkee Castle can be found at The Sea Floor after freeing Little Brother from a wriggling flytrap pellet.
It contains: