What you need is a corrugated box lined with stryrofoam like this http://www.uline.com/Browse_Listing_2157.asp. You can buy it or make your own. I doubt you need the dry ice. A good shipping box and cold packs should do.

Here is the page with the relevant info from CO.com on Dry Ice and Seafood
http://www.continental.com/web/en-US...e/fragile.aspx

Dry Ice
Continental Airlines will accept packages containing 5 lbs. (2.2 kg.) or less of dry ice as carry-on baggage or checked baggage. The container or package must be ventilated to permit the release of carbon dioxide gas. The container or package must be marked as containing dry ice and must show the net weight and the identity of the perishable item. Styrofoam coolers containing dry ice will not be accepted.

A $35.00 handling service charge applies to the transportation of dry ice as checked baggage.

Dry Ice in quantities greater than 5 lbs. (2.2 kg.) must be shipped as cargo.

Seafood
Continental Airlines will accept seafood as checked baggage if the following condition is met:

Seafood will be accepted only if it is wrapped in a sealed protective material and packed in a leak-proof container.
Seafood will not be accepted if packed in wet ice or if packed in a Styrofoam container.

Seafood carried in addition to the free baggage allowance will be assessed at the current excess baggage charge. In addition, seafood is subject to overweight and oversize charges.

Continental shall not liable for seafood. Excess Valuation may not be purchased for seafood.