Barrel sponge (Xestospongia
muta)--these sponges may live for 100 years and grow to over 18 meters tall
From NOAA-Ocean Explorer website:
"The barrel sponge (Xestospongia muta) may live for 100 years and grow to over 6 ft (18.m) tall. While populations have declined at sites throughout the Caribbean, they appear to be quite healthy on Little Cayman Island."