swimming in the sea or ocean apple watch

Hello everyone,

I want to ask something .Is it true that swimming in salt water can harm your watch’s seal agains water? .Someone told me that I have to be crazy to enter in the sea with the Watch as the salt eat the seal and after 20-30 swims I can harm the whole Watch as water will enter inside. I have the Apple Watch Ultra that is advertised to be water resistant until 100 meters and capable of diving.