The movie is about a ship with passengers , and carring a cargo of chemical that explodes on contact with water. The ship gets trapped in an area of seaweed that eats flesh.
They find people living there from the 17 to 18 th century. These people walk over the seaweed with large snow show like devices, and ballons attached to them.
The land is ruled by a young boy who is controlled by the bad guy. They feed people to a sea monster at the bottom of an old Spanish ship

Sounds like "The Lost Continent", I vaguely remember the movie being on TV years ago, but had to go to Jacks Movie Page to review the description. Jack's page says the movie was made in 1968. Hope that helps.

That name sound correct, and the date also.
Thanks, I'm going to see if I can find it.
Ap

The Lost Continent it is.