This is one of the most common White sea sponges - Halichondria panicea. These sponges live not very deep, they can grow on very different substrates. On this photo the substrate is Ascophyllum nodosum.
Underwater stones and various sinked things are often covered with the sponge Amphoriscus (Grantessa) kuekenthali.
On the depth about 4-5 m these aktinia-like sponges are very usual. Polymastia arctica (mammilaris). These yellow protuberances bear pores and sometimes osculums.
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