Exodus 26:14 reads, concerning the tabernacle “And make for the tent a covering of tanned ram skins, and a covering of dolphin skins above.” The word rendered ‘dolphin’ has not always been well-translated, since older, and unfortunately also more modern, translations often referred to these as ‘badger skins’ (cf. the King James Version) or ‘goatskins’; but, there is a good case to be made these were dolphins.
But, that demands an answer to the question, “Where did Israelite people get dolphin skins in the middle of the Sinai desert?” There are at least a few options.
(1) They traded with people from modern Qatar, who brought them up from the south.
(2) They traded with the Canaanite peoples or the Phoenicians (which seems far less likely)
(3) They brought these with them from Egypt when they ‘plundered the Egyptians’
The last option seems to me to make the most sense, seeing that Egypt probably traded with Mediterranean peoples. The picture attached to this post is actually from an island in the Mediterranean, Knossos, and was dated to c. 1500 B.C., about the same time the Israelites left Egypt.
All this makes it plausible the Israelites had access to dolphin leather, dyed blue, for the ceiling of the tabernacle (representing ‘the waters of the sky’).