20,000 Baseball Cards Under the SeaBook - 1991
Roger's friend Kenneth uses an unusual sea vehicle of his own design to take them to an underwater cave, where a cache of old loot gathered by the mermaids turns out to contain a lot of very valuable old baseball cards.
Publisher: New York : Random House, c1991.
Characteristics: 47 p. :,col. ill. ;,24 cm.
Alternative Title: Twenty thousand baseball cards under the sea.