An improvement is disclosed in apparatus of the type including a base anchored to a submerged bottom, an elongated tower provided with a buoyancy chamber near its upper end, and a pivot assembly that connects the tower to the base and permits the tower to sway in response to environmental forces. The improvement resides in a fluid tight, open bottom housing connected to said tower and adapted to enclose the pivot assembly in a bath of a lubricant, regardless of the angle of tower sway.