By using strings of pearls on fishbones. To the effect of something like this: https://en.wikipedia.org/wiki/Quipu https://en.wikipedia.org/wiki/Quipu Or selec

By using strings of pearls on fishbones. To the effect of something like this: https://en.wikipedia.org/wiki/Quipu https://en.wikipedia.org/wiki/Quipu Or selectively breeding barnacles to make longlasting letters/symbols, or 'milking' their glue and put it on something to avoid being overgrown. Imagine an aquatic market for underwater fonts!1!!