“dugongs.” Dugongs are very similar to manatees but live in the Red Sea and Gulf of Aqaba (cp. HCSB: “manatee skins”). The Hebrew word is tachash (#08476 תַּחַשׁ), and the meaning is disputed. Likely possibilities include leather from Egypt, seal skins, and the skin of dugongs. We favor dugongs for several different reasons.
God gave the instructions to Moses when they were near Sinai, so they would have been in the desert, but the Red Sea and Gulf of Aqaba was fairly close by. In order not to have to piece an immense number of skins together, the leather pieces would have had to be of large size. An adult dugong is about 10 feet long (over 3 meters), and fat around, so a single skin would cover a lot of area. This may also explain why the Tent of Meeting, which was very large, was to be covered by a number of skins (the word tachash is plural in Exod. 25:5, 26:14, 36:19; 39:34), but apparently it only took one skin to cover the ark of the covenant and the articles of the Tent of Meeting such as the table of the bread of the presence (the word tachash is singular in Num. 4:6, 8, 10, 11, 12 and 4:14. It is also singular in Num. 4:25, but in that case, it refers to the single large covering made of skins, not a single skin).
Another reason for favoring the dugong is that Ezekiel 16:10 mentions sandals made of that skin, and historians and customs experts tell us that the dugong “was once plentiful in the Gulf of Aqaba and until early in the last century its skin was the standard material for making sandals in the E. Sinai peninsula” (Merrill Tenney, ed., The Zondervan Pictorial Encyclopedia of the Bible, Regency Reference Library, Grand Rapids, MI, 1976, “Badger” p. 451).
Another reason for thinking that the dugong is what the word tachash refers to is that the other possibilities seem to eliminate themselves. Although older translations say “badger’s skins,” that does not seem possible and almost no modern translation (the NKJV excepted) goes with that translation. Some translations say “goatskins,” but there is a more natural word for goatskins that it seems God would have used in the Bible if He meant goatskins, and besides, it would have taken an immense number of goats to cover the Tent of Meeting, and furthermore a single skin could not cover the ark of the covenant or the other furniture in the Tent of Meeting.
Some translations say “seal skins,” “dolphin skins,” or “porpoise skins,” but those animals were hard to catch and therefore were rarely caught, they did not have large skins, and they were not regularly used for sandals. In contrast, the dugongs were abundant, were social and traveled (swam slowly) in groups, and were easy to hunt because they could not move fast. That leaves the second most likely possible meaning for tachash to be some kind of leather from Egypt, but although that is possible, it seems less likely to us than the skin of the dugong, in part because of the way God uses the singular and plural when referring to the skins that would cover the Tent of Meeting and the items such as the ark of the covenant.