With the exception of the more straightforward watercolor (images above, bottom), the rest of these wild and wonderfully realized watercolor illustrations are designs for New Orleans carnival parade floats from the early part of the 20th century by Swedish/American artist Bror Anders Wikstrom.
Wikstrom originally went to sea as a young man, but his career as a sailor was curtailed by changes in his eyesight. Nearsightedness did not prevent him from pursuing studies in art in Stockholm and Paris, and he applied his artistic learning to magazine illustrations, advertising design, prints, cartoons, murals and portraits.
Coming to the U.S., he settled in New Orleans and became noted for his designs for carnival floats for two of the prominent krews, Rex and Proteus.
A number of his float designs are maritime in nature, others are wilder fantasy, often featuring dragons and other fantastical creatures.
He also painted landscapes and marine paintings, though I can’t find as many examples of those; you can find some on Artnet and Invaluable (and here).