filling ballast of this SMB with seawater?

[ballastbelly]

i got one of these

scubastore.com/images/products/media/bestdivers_04348.jpg

it has 1 valve on top for air & other on bottom for water

but i can not figure out how to fill the bottom when at the sea side. no amount of holding the smb under water, inflated or not will get any water inside. am i supposed to use a syringe or something? thanks

 

[ballastbelly]

if you need to see the smb you need to put the http www etc
in front of the link, or else their home page will come up.