end 506 a of which opens in a top portion of the u201c buoyancy tank u201d 502 the duct 506 is connected through a hose 505 to the u201c pressure chamber u201d 208 fig2 a with control devices preferably located thereat for varying the pneumatic pressure in the buoyancy tank by varying the pneumatic pressure in the u201c buoyancy tank u201d 502 water is pushed in out through a u201c water breathing tube u201d 507 a top end of which is fixedly attached to the bottom of the u201c buoyancy tank u201d 502 and a lower end opening into the sea below consequently varying the u201c inlet u201d buoyancy thereby controlling the air and water intake timing and volume the rest of the arrangements of this embodiment remain similar to those described in fig4 above including an u201c inflexible pipe u201d 503 connected to a u201c flexible pipe u201d 504 a u201c ballast u201d 508 attached to the tube 507 a mooring ring 509 attached at the bottom of the tube 507 and a mooring line 510 attached to the ring 509 in another embodiment an u201c inlet u201d apparatus 601 which is illustrated by fig6 includes an u201c inflatable buoyancy tank u201d 602 which is directly connected with a pneumatic hose 605 as above but without the u201c pneumatic duct u201d and u201c water breathing tube u201d the rest of the arrangements being similar to the previous embodiment described in the above paragraph the hose 605 terminates at a duct 606 inside the tank 602 an u201c inflexible pipe u201d.